Port some examples on Python 2

14 files changed, 158 insertions, 111 deletions

diff --git a/TODO b/TODO
index f884b45..6c117ba 100644
--- a/TODO
+++ b/TODO
@@ -5,6 +5,12 @@
   - test_queues.py
   - test_tasks.py
 
+* Fix examples:
+
+  - cacheclt/cachesrv.py
+  - source1.py: 'StreamWriter' object has no attribute '_writer'
+  - stacks.py: 'exceptions.ZeroDivisionError' object has no attribute '__traceback__'
+
 * as_completed() is a coroutine or not?
 * Move asyncio/coroutine.py in asyncio/tasks.py?
 * Fix coroutine._DEBUG=True
diff --git a/examples/child_process.py b/examples/child_process.py
index 4410414..76bd04d 100644
--- a/examples/child_process.py
+++ b/examples/child_process.py
@@ -31,8 +31,8 @@ else:
 def connect_write_pipe(file):
     loop = asyncio.get_event_loop()
     protocol = protocols.Protocol()
-    transport, _ =  yield from loop.connect_write_pipe(asyncio.Protocol, file)
-    return transport
+    transport, _ =  yield loop.connect_write_pipe(asyncio.Protocol, file)
+    raise asyncio.Return(transport)
 
 #
 # Wrap a readable pipe in a stream
@@ -44,8 +44,8 @@ def connect_read_pipe(file):
     stream_reader = streams.StreamReader(loop=loop)
     def factory():
         return streams.StreamReaderProtocol(stream_reader)
-    transport, _ = yield from loop.connect_read_pipe(factory, file)
-    return stream_reader, transport
+    transport, _ = yield loop.connect_read_pipe(factory, file)
+    raise asyncio.Return((stream_reader, transport))
 
 
 #
@@ -82,9 +82,9 @@ def main(loop):
     p = Popen([sys.executable, '-c', code],
               stdin=PIPE, stdout=PIPE, stderr=PIPE)
 
-    stdin = yield from connect_write_pipe(p.stdin)
-    stdout, stdout_transport = yield from connect_read_pipe(p.stdout)
-    stderr, stderr_transport = yield from connect_read_pipe(p.stderr)
+    stdin = yield connect_write_pipe(p.stdin)
+    stdout, stdout_transport = yield connect_read_pipe(p.stdout)
+    stderr, stderr_transport = yield connect_read_pipe(p.stderr)
 
     # interact with subprocess
     name = {stdout:'OUT', stderr:'ERR'}
@@ -102,7 +102,7 @@ def main(loop):
         # get and print lines from stdout, stderr
         timeout = None
         while registered:
-            done, pending = yield from asyncio.wait(
+            done, pending = yield asyncio.wait(
                 registered, timeout=timeout,
                 return_when=asyncio.FIRST_COMPLETED)
             if not done:
diff --git a/examples/fetch0.py b/examples/fetch0.py
index 180fcf2..371acfb 100644
--- a/examples/fetch0.py
+++ b/examples/fetch0.py
@@ -1,5 +1,6 @@
 """Simplest possible HTTP client."""
 
+from __future__ import print_function
 import sys
 
 from asyncio import *
@@ -7,19 +8,19 @@ from asyncio import *
 
 @coroutine
 def fetch():
-    r, w = yield from open_connection('python.org', 80)
+    r, w = yield open_connection('python.org', 80)
     request = 'GET / HTTP/1.0\r\n\r\n'
     print('>', request, file=sys.stderr)
     w.write(request.encode('latin-1'))
     while True:
-        line = yield from r.readline()
+        line = yield r.readline()
         line = line.decode('latin-1').rstrip()
         if not line:
             break
         print('<', line, file=sys.stderr)
     print(file=sys.stderr)
-    body = yield from r.read()
-    return body
+    body = yield r.read()
+    raise Return(body)
 
 
 def main():
diff --git a/examples/fetch1.py b/examples/fetch1.py
index 8dbb6e4..fdf559d 100644
--- a/examples/fetch1.py
+++ b/examples/fetch1.py
@@ -3,8 +3,12 @@
 This version adds URL parsing (including SSL) and a Response object.
 """
 
+from __future__ import print_function
 import sys
-import urllib.parse
+try:
+    from urllib.parse import urlparse
+except ImportError:
+    from urlparse import urlparse
 
 from asyncio import *
 
@@ -22,13 +26,13 @@ class Response:
     def read(self, reader):
         @coroutine
         def getline():
-            return (yield from reader.readline()).decode('latin-1').rstrip()
-        status_line = yield from getline()
+            raise Return((yield reader.readline()).decode('latin-1').rstrip())
+        status_line = yield getline()
         if self.verbose: print('<', status_line, file=sys.stderr)
         self.http_version, status, self.reason = status_line.split(None, 2)
         self.status = int(status)
         while True:
-            header_line = yield from getline()
+            header_line = yield getline()
             if not header_line:
                 break
             if self.verbose: print('<', header_line, file=sys.stderr)
@@ -40,7 +44,7 @@ class Response:
 
 @coroutine
 def fetch(url, verbose=True):
-    parts = urllib.parse.urlparse(url)
+    parts = urlparse(url)
     if parts.scheme == 'http':
         ssl = False
     elif parts.scheme == 'https':
@@ -57,12 +61,12 @@ def fetch(url, verbose=True):
     request = 'GET %s HTTP/1.0\r\n\r\n' % path
     if verbose:
         print('>', request, file=sys.stderr, end='')
-    r, w = yield from open_connection(parts.hostname, port, ssl=ssl)
+    r, w = yield open_connection(parts.hostname, port, ssl=ssl)
     w.write(request.encode('latin-1'))
     response = Response(verbose)
-    yield from response.read(r)
-    body = yield from r.read()
-    return body
+    yield response.read(r)
+    body = yield r.read()
+    raise Return(body)
 
 
 def main():
diff --git a/examples/fetch2.py b/examples/fetch2.py
index 7617b59..4096117 100644
--- a/examples/fetch2.py
+++ b/examples/fetch2.py
@@ -3,9 +3,15 @@
 This version adds a Request object.
 """
 
+from __future__ import print_function
 import sys
-import urllib.parse
-from http.client import BadStatusLine
+try:
+    from urllib.parse import urlparse
+    from http.client import BadStatusLine
+except ImportError:
+    # Python 2
+    from urlparse import urlparse
+    from httplib import BadStatusLine
 
 from asyncio import *
 
@@ -15,7 +21,7 @@ class Request:
     def __init__(self, url, verbose=True):
         self.url = url
         self.verbose = verbose
-        self.parts = urllib.parse.urlparse(self.url)
+        self.parts = urlparse(self.url)
         self.scheme = self.parts.scheme
         assert self.scheme in ('http', 'https'), repr(url)
         self.ssl = self.parts.scheme == 'https'
@@ -40,9 +46,9 @@ class Request:
             print('* Connecting to %s:%s using %s' %
                   (self.hostname, self.port, 'ssl' if self.ssl else 'tcp'),
                   file=sys.stderr)
-        self.reader, self.writer = yield from open_connection(self.hostname,
-                                                              self.port,
-                                                              ssl=self.ssl)
+        self.reader, self.writer = yield open_connection(self.hostname,
+                                                         self.port,
+                                                         ssl=self.ssl)
         if self.verbose:
             print('* Connected to %s' %
                   (self.writer.get_extra_info('peername'),),
@@ -67,8 +73,8 @@ class Request:
     @coroutine
     def get_response(self):
         response = Response(self.reader, self.verbose)
-        yield from response.read_headers()
-        return response
+        yield response.read_headers()
+        raise Return(response)
 
 
 class Response:
@@ -83,11 +89,11 @@ class Response:
 
     @coroutine
     def getline(self):
-        return (yield from self.reader.readline()).decode('latin-1').rstrip()
+        raise Return((yield self.reader.readline()).decode('latin-1').rstrip())
 
     @coroutine
     def read_headers(self):
-        status_line = yield from self.getline()
+        status_line = yield self.getline()
         if self.verbose: print('<', status_line, file=sys.stderr)
         status_parts = status_line.split(None, 2)
         if len(status_parts) != 3:
@@ -95,7 +101,7 @@ class Response:
         self.http_version, status, self.reason = status_parts
         self.status = int(status)
         while True:
-            header_line = yield from self.getline()
+            header_line = yield self.getline()
             if not header_line:
                 break
             if self.verbose: print('<', header_line, file=sys.stderr)
@@ -112,20 +118,20 @@ class Response:
                 nbytes = int(value)
                 break
         if nbytes is None:
-            body = yield from self.reader.read()
+            body = yield self.reader.read()
         else:
-            body = yield from self.reader.readexactly(nbytes)
-        return body
+            body = yield self.reader.readexactly(nbytes)
+        raise Return(body)
 
 
 @coroutine
 def fetch(url, verbose=True):
     request = Request(url, verbose)
-    yield from request.connect()
-    yield from request.send_request()
-    response = yield from request.get_response()
-    body = yield from response.read()
-    return body
+    yield request.connect()
+    yield request.send_request()
+    response = yield request.get_response()
+    body = yield response.read()
+    raise Return(body)
 
 
 def main():
@@ -134,7 +140,11 @@ def main():
         body = loop.run_until_complete(fetch(sys.argv[1], '-v' in sys.argv))
     finally:
         loop.close()
-    sys.stdout.buffer.write(body)
+    if hasattr(sys.stdout, 'buffer'):
+        sys.stdout.buffer.write(body)
+    else:
+        # Python 2
+        sys.stdout.write(body)
 
 
 if __name__ == '__main__':
diff --git a/examples/fetch3.py b/examples/fetch3.py
index 780222b..2e4b466 100644
--- a/examples/fetch3.py
+++ b/examples/fetch3.py
@@ -4,9 +4,15 @@ This version adds a primitive connection pool, redirect following and
 chunked transfer-encoding.  It also supports a --iocp flag.
 """
 
+from __future__ import print_function
 import sys
-import urllib.parse
-from http.client import BadStatusLine
+try:
+    from urllib.parse import urlparse
+    from http.client import BadStatusLine
+except ImportError:
+    # Python 2
+    from urlparse import urlparse
+    from httplib import BadStatusLine
 
 from asyncio import *
 
@@ -25,25 +31,29 @@ class ConnectionPool:
     @coroutine
     def open_connection(self, host, port, ssl):
         port = port or (443 if ssl else 80)
-        ipaddrs = yield from get_event_loop().getaddrinfo(host, port)
+        ipaddrs = yield get_event_loop().getaddrinfo(host, port)
         if self.verbose:
             print('* %s resolves to %s' %
                   (host, ', '.join(ip[4][0] for ip in ipaddrs)),
                   file=sys.stderr)
-        for _, _, _, _, (h, p, *_) in ipaddrs:
+        for _, _, _, _, parts in ipaddrs:
+            h = parts[0]
+            p = parts[1]
             key = h, p, ssl
             conn = self.connections.get(key)
             if conn:
                 if self.verbose:
                     print('* Reusing pooled connection', key, file=sys.stderr)
-                return conn
-        reader, writer = yield from open_connection(host, port, ssl=ssl)
-        host, port, *_ = writer.get_extra_info('peername')
+                raise Return(conn)
+        reader, writer = yield open_connection(host, port, ssl=ssl)
+        parts = writer.get_extra_info('peername')
+        host = parts[0]
+        port = parts[1]
         key = host, port, ssl
         self.connections[key] = reader, writer
         if self.verbose:
             print('* New connection', key, file=sys.stderr)
-        return reader, writer
+        raise Return((reader, writer))
 
 
 class Request:
@@ -51,7 +61,7 @@ class Request:
     def __init__(self, url, verbose=True):
         self.url = url
         self.verbose = verbose
-        self.parts = urllib.parse.urlparse(self.url)
+        self.parts = urlparse(self.url)
         self.scheme = self.parts.scheme
         assert self.scheme in ('http', 'https'), repr(url)
         self.ssl = self.parts.scheme == 'https'
@@ -79,7 +89,7 @@ class Request:
         self.vprint('* Connecting to %s:%s using %s' %
                     (self.hostname, self.port, 'ssl' if self.ssl else 'tcp'))
         self.reader, self.writer = \
-                     yield from pool.open_connection(self.hostname,
+                     yield pool.open_connection(self.hostname,
                                                      self.port,
                                                      ssl=self.ssl)
         self.vprint('* Connected to %s' %
@@ -89,24 +99,24 @@ class Request:
     def putline(self, line):
         self.vprint('>', line)
         self.writer.write(line.encode('latin-1') + b'\r\n')
-        ##yield from self.writer.drain()
+        ##yield self.writer.drain()
 
     @coroutine
     def send_request(self):
         request = '%s %s %s' % (self.method, self.full_path, self.http_version)
-        yield from self.putline(request)
+        yield self.putline(request)
         if 'host' not in {key.lower() for key, _ in self.headers}:
             self.headers.insert(0, ('Host', self.netloc))
         for key, value in self.headers:
             line = '%s: %s' % (key, value)
-            yield from self.putline(line)
-        yield from self.putline('')
+            yield self.putline(line)
+        yield self.putline('')
 
     @coroutine
     def get_response(self):
         response = Response(self.reader, self.verbose)
-        yield from response.read_headers()
-        return response
+        yield response.read_headers()
+        raise Return(response)
 
 
 class Response:
@@ -125,20 +135,20 @@ class Response:
 
     @coroutine
     def getline(self):
-        line = (yield from self.reader.readline()).decode('latin-1').rstrip()
+        line = (yield self.reader.readline()).decode('latin-1').rstrip()
         self.vprint('<', line)
-        return line
+        raise Return(line)
 
     @coroutine
     def read_headers(self):
-        status_line = yield from self.getline()
+        status_line = yield self.getline()
         status_parts = status_line.split(None, 2)
         if len(status_parts) != 3:
             raise BadStatusLine(status_line)
         self.http_version, status, self.reason = status_parts
         self.status = int(status)
         while True:
-            header_line = yield from self.getline()
+            header_line = yield self.getline()
             if not header_line:
                 break
             # TODO: Continuation lines.
@@ -168,24 +178,24 @@ class Response:
             if self.get_header('transfer-encoding', '').lower() == 'chunked':
                 blocks = []
                 while True:
-                    size_header = yield from self.reader.readline()
+                    size_header = yield self.reader.readline()
                     if not size_header:
                         break
                     parts = size_header.split(b';')
                     size = int(parts[0], 16)
                     if not size:
                         break
-                    block = yield from self.reader.readexactly(size)
+                    block = yield self.reader.readexactly(size)
                     assert len(block) == size, (len(block), size)
                     blocks.append(block)
-                    crlf = yield from self.reader.readline()
+                    crlf = yield self.reader.readline()
                     assert crlf == b'\r\n'
                 body = b''.join(blocks)
             else:
-                body = yield from self.reader.read()
+                body = yield self.reader.read()
         else:
-            body = yield from self.reader.readexactly(nbytes)
-        return body
+            body = yield self.reader.readexactly(nbytes)
+        raise Return(body)
 
 
 @coroutine
@@ -194,16 +204,16 @@ def fetch(url, verbose=True, max_redirect=10):
     try:
         for _ in range(max_redirect):
             request = Request(url, verbose)
-            yield from request.connect(pool)
-            yield from request.send_request()
-            response = yield from request.get_response()
-            body = yield from response.read()
+            yield request.connect(pool)
+            yield request.send_request()
+            response = yield request.get_response()
+            body = yield response.read()
             next_url = response.get_redirect_url()
             if not next_url:
                 break
             url = urllib.parse.urljoin(url, next_url)
             print('redirect to', url, file=sys.stderr)
-        return body
+        raise Return(body)
     finally:
         pool.close()
 
@@ -219,7 +229,11 @@ def main():
         body = loop.run_until_complete(fetch(sys.argv[1], '-v' in sys.argv))
     finally:
         loop.close()
-    sys.stdout.buffer.write(body)
+    if hasattr(sys.stdout, 'buffer'):
+        sys.stdout.buffer.write(body)
+    else:
+        # Python 2
+        sys.stdout.write(body)
 
 
 if __name__ == '__main__':
diff --git a/examples/hello_coroutine.py b/examples/hello_coroutine.py
index 8ad682d..e2c03dc 100644
--- a/examples/hello_coroutine.py
+++ b/examples/hello_coroutine.py
@@ -7,7 +7,7 @@ import asyncio
 def greet_every_two_seconds():
     while True:
         print('Hello World')
-        yield from asyncio.sleep(2)
+        yield asyncio.sleep(2)
 
 
 if __name__ == '__main__':
diff --git a/examples/simple_tcp_server.py b/examples/simple_tcp_server.py
index c36710d..b05052b 100644
--- a/examples/simple_tcp_server.py
+++ b/examples/simple_tcp_server.py
@@ -8,6 +8,7 @@ in the same process.  It listens on port 1234 on 127.0.0.1, so it will
 fail if this port is currently in use.
 """
 
+from __future__ import print_function
 import sys
 import asyncio
 import asyncio.streams
@@ -58,10 +59,12 @@ class MyServer:
         out one or more lines back to the client with the result.
         """
         while True:
-            data = (yield from client_reader.readline()).decode("utf-8")
+            data = (yield client_reader.readline()).decode("utf-8")
             if not data: # an empty string means the client disconnected
                 break
-            cmd, *args = data.rstrip().split(' ')
+            parts = data.rstrip().split(' ')
+            cmd = parts[0]
+            args = parts[1:]
             if cmd == 'add':
                 arg1 = float(args[0])
                 arg2 = float(args[1])
@@ -79,7 +82,7 @@ class MyServer:
                 print("Bad command {!r}".format(data), file=sys.stderr)
 
             # This enables us to have flow control in our connection.
-            yield from client_writer.drain()
+            yield client_writer.drain()
 
     def start(self, loop):
         """
@@ -115,7 +118,7 @@ def main():
 
     @asyncio.coroutine
     def client():
-        reader, writer = yield from asyncio.streams.open_connection(
+        reader, writer = yield asyncio.streams.open_connection(
             '127.0.0.1', 12345, loop=loop)
 
         def send(msg):
@@ -123,24 +126,24 @@ def main():
             writer.write((msg + '\n').encode("utf-8"))
 
         def recv():
-            msgback = (yield from reader.readline()).decode("utf-8").rstrip()
+            msgback = (yield reader.readline()).decode("utf-8").rstrip()
             print("< " + msgback)
-            return msgback
+            raise asyncio.Return(msgback)
 
         # send a line
         send("add 1 2")
-        msg = yield from recv()
+        msg = yield recv()
 
         send("repeat 5 hello")
-        msg = yield from recv()
+        msg = yield recv()
         assert msg == 'begin'
         while True:
-            msg = yield from recv()
+            msg = yield recv()
             if msg == 'end':
                 break
 
         writer.close()
-        yield from asyncio.sleep(0.5)
+        yield asyncio.sleep(0.5)
 
     # creates a client and connects to our server
     msg = loop.run_until_complete(client())
diff --git a/examples/sink.py b/examples/sink.py
index d362cbb..b3ac3e8 100644
--- a/examples/sink.py
+++ b/examples/sink.py
@@ -1,5 +1,6 @@
 """Test service that accepts connections and reads all data off them."""
 
+from __future__ import print_function
 import argparse
 import os
 import sys
@@ -64,15 +65,16 @@ def start(loop, host, port):
         # TODO: take cert/key from args as well.
         here = os.path.join(os.path.dirname(__file__), '..', 'tests')
         sslctx = ssl.SSLContext(ssl.PROTOCOL_SSLv23)
-        sslctx.options |= ssl.OP_NO_SSLv2
+        if hasattr(sslctx, 'options'):
+            sslctx.options |= ssl.OP_NO_SSLv2
         sslctx.load_cert_chain(
             certfile=os.path.join(here, 'ssl_cert.pem'),
             keyfile=os.path.join(here, 'ssl_key.pem'))
 
-    server = yield from loop.create_server(Service, host, port, ssl=sslctx)
+    server = yield loop.create_server(Service, host, port, ssl=sslctx)
     dprint('serving TLS' if sslctx else 'serving',
            [s.getsockname() for s in server.sockets])
-    yield from server.wait_closed()
+    yield server.wait_closed()
 
 
 def main():
diff --git a/examples/source.py b/examples/source.py
index 7fd11fb..38f678a 100644
--- a/examples/source.py
+++ b/examples/source.py
@@ -1,5 +1,6 @@
 """Test client that connects and sends infinite data."""
 
+from __future__ import print_function
 import argparse
 import sys
 
@@ -74,11 +75,11 @@ def start(loop, host, port):
     sslctx = None
     if args.tls:
         sslctx = test_utils.dummy_ssl_context()
-    tr, pr = yield from loop.create_connection(Client, host, port,
-                                               ssl=sslctx)
+    tr, pr = yield loop.create_connection(Client, host, port,
+                                          ssl=sslctx)
     dprint('tr =', tr)
     dprint('pr =', pr)
-    yield from pr.waiter
+    yield pr.waiter
 
 
 def main():
diff --git a/examples/source1.py b/examples/source1.py
index 6802e96..5316506 100644
--- a/examples/source1.py
+++ b/examples/source1.py
@@ -1,5 +1,6 @@
 """Like source.py, but uses streams."""
 
+from __future__ import print_function
 import argparse
 import sys
 
@@ -33,7 +34,7 @@ class Debug:
     overwriting = False
     label = 'stream1:'
 
-    def print(self, *args):
+    def print_(self, *args):
         if self.overwriting:
             print(file=sys.stderr)
             self.overwriting = 0
@@ -46,7 +47,8 @@ class Debug:
             if self.overwriting == 3:
                 print(self.label, '[...]', file=sys.stderr)
             end = '\r'
-        print(self.label, *args, file=sys.stderr, end=end, flush=True)
+        print(self.label, *args, file=sys.stderr, end=end)
+        sys.stdout.flush()
 
 
 @coroutine
@@ -55,11 +57,11 @@ def start(loop, args):
     total = 0
     sslctx = None
     if args.tls:
-        d.print('using dummy SSLContext')
+        d.print_('using dummy SSLContext')
         sslctx = test_utils.dummy_ssl_context()
-    r, w = yield from open_connection(args.host, args.port, ssl=sslctx)
-    d.print('r =', r)
-    d.print('w =', w)
+    r, w = yield open_connection(args.host, args.port, ssl=sslctx)
+    d.print_('r =', r)
+    d.print_('w =', w)
     if args.stop:
         w.write(b'stop')
         w.close()
@@ -73,10 +75,10 @@ def start(loop, args):
                 w.write(data)
                 f = w.drain()
                 if f:
-                    d.print('pausing')
-                    yield from f
+                    d.print_('pausing')
+                    yield f
         except (ConnectionResetError, BrokenPipeError) as exc:
-            d.print('caught', repr(exc))
+            d.print_('caught', repr(exc))
 
 
 def main():
diff --git a/examples/stacks.py b/examples/stacks.py
index 371d31f..eff73c3 100644
--- a/examples/stacks.py
+++ b/examples/stacks.py
@@ -10,9 +10,9 @@ def helper(r):
     for t in Task.all_tasks():
         t.print_stack()
     print('--- end helper ---')
-    line = yield from r.readline()
+    line = yield r.readline()
     1/0
-    return line
+    raise Return(line)
 
 def doit():
     l = get_event_loop()
diff --git a/examples/timing_tcp_server.py b/examples/timing_tcp_server.py
index 6f0483e..6755ab1 100644
--- a/examples/timing_tcp_server.py
+++ b/examples/timing_tcp_server.py
@@ -8,6 +8,7 @@ in the same process.  It listens on port 1234 on 127.0.0.1, so it will
 fail if this port is currently in use.
 """
 
+from __future__ import print_function
 import sys
 import time
 import random
@@ -61,10 +62,12 @@ class MyServer:
         out one or more lines back to the client with the result.
         """
         while True:
-            data = (yield from client_reader.readline()).decode("utf-8")
+            data = (yield client_reader.readline()).decode("utf-8")
             if not data: # an empty string means the client disconnected
                 break
-            cmd, *args = data.rstrip().split(' ')
+            parts = data.rstrip().split(' ')
+            cmd = parts[0]
+            args = parts[1:]
             if cmd == 'add':
                 arg1 = float(args[0])
                 arg2 = float(args[1])
@@ -83,7 +86,7 @@ class MyServer:
                 print("Bad command {!r}".format(data), file=sys.stderr)
 
             # This enables us to have flow control in our connection.
-            yield from client_writer.drain()
+            yield client_writer.drain()
 
     def start(self, loop):
         """
@@ -119,7 +122,7 @@ def main():
 
     @asyncio.coroutine
     def client():
-        reader, writer = yield from asyncio.streams.open_connection(
+        reader, writer = yield asyncio.streams.open_connection(
             '127.0.0.1', 12345, loop=loop)
 
         def send(msg):
@@ -127,13 +130,13 @@ def main():
             writer.write((msg + '\n').encode("utf-8"))
 
         def recv():
-            msgback = (yield from reader.readline()).decode("utf-8").rstrip()
+            msgback = (yield reader.readline()).decode("utf-8").rstrip()
             print("< " + msgback)
-            return msgback
+            raise asyncio.Return(msgback)
 
         # send a line
         send("add 1 2")
-        msg = yield from recv()
+        msg = yield recv()
 
         Ns = list(range(100, 100000, 10000))
         times = []
@@ -141,10 +144,10 @@ def main():
         for N in Ns:
             t0 = time.time()
             send("repeat {} hello world ".format(N))
-            msg = yield from recv()
+            msg = yield recv()
             assert msg == 'begin'
             while True:
-                msg = (yield from reader.readline()).decode("utf-8").rstrip()
+                msg = (yield reader.readline()).decode("utf-8").rstrip()
                 if msg == 'end':
                     break
             t1 = time.time()
@@ -154,7 +157,7 @@ def main():
             times.append(dt)
 
         writer.close()
-        yield from asyncio.sleep(0.5)
+        yield asyncio.sleep(0.5)
 
     # creates a client and connects to our server
     msg = loop.run_until_complete(client())
diff --git a/runtests.py b/runtests.py
index 469ac86..59710b8 100644
--- a/runtests.py
+++ b/runtests.py
@@ -19,6 +19,7 @@ runtests.py --coverage is equivalent of:
 
 # Originally written by Beech Horn (for NDB).
 
+from __future__ import print_function
 import argparse
 import gc
 import logging