cli.updater: Reduce verbosity when getting network errors.

Show the error message without a traceback.

caucase/cli.py

@@ -28,7 +28,6 @@ import os
 import socket
 import struct
 import sys
-import traceback
 from cryptography import x509
 from cryptography.hazmat.backends import default_backend
 from . import exceptions
@@ -70,10 +69,14 @@ class RetryingCaucaseClient(CaucaseClient):
         httplib.LineTooLong,
         httplib.UnknownProtocol,
         httplib.IncompleteRead,
-      ):
+        ) as exception:
         connection.close() # Resets HTTPConnection state machine.
-        print('Got a network error, retrying in a bit...')
-        traceback.print_exc()
+        # Note: repr(str(exception)) is nicer than repr(exception), without
+        # letting non-printable characters through.
+        print('Got a network error, retrying in a bit: %s: %r' % (
+          exception.__class__.__name__,
+          str(exception),
+        ))
         self._until(datetime.datetime.now() + datetime.timedelta(0, 10))
 
 _cryptography_backend = default_backend()