Raise usefully ambiguous error when every connect attempt fails.

Re #22

1 files changed, 30 insertions, 0 deletions

diff --git a/paramiko/ssh_exception.py b/paramiko/ssh_exception.py
index b99e42b3..7e6f2568 100644
--- a/paramiko/ssh_exception.py
+++ b/paramiko/ssh_exception.py
@@ -16,6 +16,8 @@
 # along with Paramiko; if not, write to the Free Software Foundation, Inc.,
 # 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA.
 
+import socket
+
 
 class SSHException (Exception):
     """
@@ -129,3 +131,31 @@ class ProxyCommandFailure (SSHException):
         self.error = error
         # for unpickling
         self.args = (command, error, )
+
+
+class ConnectionError(socket.error):
+    """
+    High-level socket error wrapping 1+ actual socket.error objects.
+    
+    To see the wrapped exception objects, access the ``errors`` attribute.
+    ``errors`` is a dict whose keys are address tuples (e.g. ``('127.0.0.1',
+    22)``) and whose values are the exception encountered trying to connect to
+    that address.
+
+    It is implied/assumed that all the errors given to a single instance of
+    this class are from connecting to the same hostname + port (and thus that
+    the differences are in the resolution of the hostname - e.g. IPv4 vs v6).
+    """
+    def __init__(self, errors):
+        """
+        :param dict errors:
+            The errors dict to store, as described by class docstring.
+        """
+        addrs = errors.keys()
+        body = ', '.join([x[0] for x in addrs[:-1]])
+        tail = addrs[-1][0]
+        msg = "Unable to connect to port {0} at {1} or {2}"
+        super(ConnectionError, self).__init__(
+            msg.format(addrs[0][1], body, tail)
+        )
+        self.errors = errors