Update conn.py to catch OSError in case of failed import (dpkp#2407)

Closes dpkp#2399.

kafka/conn.py

@@ -78,7 +78,7 @@ class SSLWantWriteError(Exception):
 try:
     import gssapi
     from gssapi.raw.misc import GSSError
-except ImportError:
+except (ImportError, OSError):
     #no gssapi available, will disable gssapi mechanism
     gssapi = None
     GSSError = None