Make send() and recv() fail when channel is closed

``sendall()`` was checking if the channel has been closed, 
and failed accordingly, but ``send()`` and ``recv()`` did not.
This meant that ``chan.send("foo")`` when the channel was already
closed, just blocked forever.

paramiko/channel.py

@@ -605,6 +605,10 @@ class Channel (object):
         @raise socket.timeout: if no data is ready before the timeout set by
             L{settimeout}.
         """
+        if self.closed:
+            # this doesn't seem useful, but it is the documented behavior of Socket
+            raise socket.error(errno.EBADF, 'Socket is closed')
+
         try:
             out = self.in_buffer.read(nbytes, self.timeout)
         except PipeTimeout, e:
@@ -655,6 +659,10 @@ class Channel (object):
         
         @since: 1.1
         """
+        if self.closed:
+            # this doesn't seem useful, but it is the documented behavior of Socket
+            raise socket.error(errno.EBADF, 'Socket is closed')
+
         try:
             out = self.in_stderr_buffer.read(nbytes, self.timeout)
         except PipeTimeout, e:
@@ -708,6 +716,10 @@ class Channel (object):
         @raise socket.timeout: if no data could be sent before the timeout set
             by L{settimeout}.
         """
+        if self.closed:
+            # this doesn't seem useful, but it is the documented behavior of Socket
+            raise socket.error(errno.EBADF, 'Socket is closed')
+
         size = len(s)
         self.lock.acquire()
         try:
@@ -745,6 +757,10 @@ class Channel (object):
         
         @since: 1.1
         """
+        if self.closed:
+            # this doesn't seem useful, but it is the documented behavior of Socket
+            raise socket.error(errno.EBADF, 'Socket is closed')
+
         size = len(s)
         self.lock.acquire()
         try:
@@ -783,9 +799,6 @@ class Channel (object):
             This is irritating, but identically follows python's API.
         """
         while s:
-            if self.closed:
-                # this doesn't seem useful, but it is the documented behavior of Socket
-                raise socket.error('Socket is closed')
             sent = self.send(s)
             s = s[sent:]
         return None