Merge branch '2.0' into 2.1

3 files changed, 19 insertions, 20 deletions

diff --git a/paramiko/common.py b/paramiko/common.py
index 556f046a..0012372a 100644
--- a/paramiko/common.py
+++ b/paramiko/common.py
@@ -20,9 +20,7 @@
 Common constants and global variables.
 """
 import logging
-from paramiko.py3compat import (
-    byte_chr, PY2, bytes_types, string_types, b, long,
-)
+from paramiko.py3compat import byte_chr, PY2, bytes_types, text_type, long
 
 MSG_DISCONNECT, MSG_IGNORE, MSG_UNIMPLEMENTED, MSG_DEBUG, \
     MSG_SERVICE_REQUEST, MSG_SERVICE_ACCEPT = range(1, 7)
@@ -163,14 +161,16 @@ else:
 
 
 def asbytes(s):
-    if not isinstance(s, bytes_types):
-        if isinstance(s, string_types):
-            s = b(s)
-        else:
-            try:
-                s = s.asbytes()
-            except Exception:
-                raise Exception('Unknown type')
+    """Coerce to bytes if possible or return unchanged."""
+    if isinstance(s, bytes_types):
+        return s
+    if isinstance(s, text_type):
+        # Accept text and encode as utf-8 for compatibility only.
+        return s.encode("utf-8")
+    asbytes = getattr(s, "asbytes", None)
+    if asbytes is not None:
+        return asbytes()
+    # May be an object that implements the buffer api, let callers handle.
     return s
 
 
diff --git a/paramiko/file.py b/paramiko/file.py
index 5212091a..a1bdafbe 100644
--- a/paramiko/file.py
+++ b/paramiko/file.py
@@ -18,7 +18,7 @@
 from paramiko.common import (
     linefeed_byte_value, crlf, cr_byte, linefeed_byte, cr_byte_value,
 )
-from paramiko.py3compat import BytesIO, PY2, u, b, bytes_types
+from paramiko.py3compat import BytesIO, PY2, u, bytes_types, text_type
 
 from paramiko.util import ClosingContextManager
 
@@ -391,7 +391,9 @@ class BufferedFile (ClosingContextManager):
 
         :param data: ``str``/``bytes`` data to write
         """
-        data = b(data)
+        if isinstance(data, text_type):
+            # Accept text and encode as utf-8 for compatibility only.
+            data = data.encode('utf-8')
         if self._closed:
             raise IOError('File is closed')
         if not (self._flags & self.FLAG_WRITE):
diff --git a/paramiko/sftp_client.py b/paramiko/sftp_client.py
index 12fccb2f..ee5ab073 100644
--- a/paramiko/sftp_client.py
+++ b/paramiko/sftp_client.py
@@ -28,9 +28,7 @@ from paramiko import util
 from paramiko.channel import Channel
 from paramiko.message import Message
 from paramiko.common import INFO, DEBUG, o777
-from paramiko.py3compat import (
-    bytestring, b, u, long, string_types, bytes_types,
-)
+from paramiko.py3compat import bytestring, b, u, long
 from paramiko.sftp import (
     BaseSFTP, CMD_OPENDIR, CMD_HANDLE, SFTPError, CMD_READDIR, CMD_NAME,
     CMD_CLOSE, SFTP_FLAG_READ, SFTP_FLAG_WRITE, SFTP_FLAG_CREATE,
@@ -758,13 +756,12 @@ class SFTPClient(BaseSFTP, ClosingContextManager):
                     msg.add_int64(item)
                 elif isinstance(item, int):
                     msg.add_int(item)
-                elif isinstance(item, (string_types, bytes_types)):
-                    msg.add_string(item)
                 elif isinstance(item, SFTPAttributes):
                     item._pack(msg)
                 else:
-                    raise Exception(
-                        'unknown type for %r type %r' % (item, type(item)))
+                    # For all other types, rely on as_string() to either coerce
+                    # to bytes before writing or raise a suitable exception.
+                    msg.add_string(item)
             num = self.request_number
             self._expecting[num] = fileobj
             self.request_number += 1