Handle communication failures cleanly

Expand exceptions to cover more failures cases. This adds
CommunicationFailure to represent any failures while attempting
to communicate with the remote endpoint. This also adds a new base
exception class BaseException which should be used for all non-HTTP
related failures.

Change-Id: Ie3e1d45c520d816a3f491a85fde94a6c4edf295e

glanceclient/common/http.py

@@ -75,7 +75,11 @@ class HTTPClient(object):
 
     def get_connection(self):
         _class = self.connection_params[0]
-        return _class(*self.connection_params[1], **self.connection_params[2])
+        try:
+            return _class(*self.connection_params[1],
+                          **self.connection_params[2])
+        except httplib.InvalidUrl:
+            raise exc.InvalidEndpoint()
 
     def log_curl_request(self, method, url, kwargs):
         curl = ['curl -i -X %s' % method]
@@ -126,10 +130,17 @@ class HTTPClient(object):
             kwargs['headers'].setdefault('X-Auth-Token', self.auth_token)
 
         self.log_curl_request(method, url, kwargs)
-
         conn = self.get_connection()
+
+        try:
             conn.request(method, url, **kwargs)
+        except (socket.error, socket.gaierror):
+            raise exc.InvalidEndpoint()
+
+        try:
             resp = conn.getresponse()
+        except (socket.error, socket.timeout):
+            raise exc.CommunicationError()
 
         body_iter = ResponseBodyIterator(resp)
 

glanceclient/exc.py

@@ -16,14 +16,25 @@
 import sys
 
 
-class CommandError(Exception):
+class BaseException(Exception):
+    """An error occurred."""
+    def __init__(self, message=None):
+        self.message = message
+
+    def __str__(self):
+        return self.message or self.__class__.__doc__
+
+
+class CommandError(BaseException):
     """Invalid usage of CLI"""
-    pass
 
 
-class InvalidEndpoint(ValueError):
+class InvalidEndpoint(BaseException):
-    """The provided endpoint could not be used"""
+    """The provided endpoint is invalid."""
-    pass
+
+
+class CommunicationError(BaseException):
+    """Unable to communicate with server."""
 
 
 class ClientException(Exception):