diff --git a/apiclient/oauth.py b/apiclient/oauth.py
index de20336..9907c46 100644
--- a/apiclient/oauth.py
+++ b/apiclient/oauth.py
@@ -131,10 +131,9 @@
         headers = {}
       headers.update(req.to_header())
       if 'user-agent' in headers:
-        headers['user-agent'] += ' '
+        headers['user-agent'] =  self.user_agent + ' ' + headers['user-agent']
       else:
-        headers['user-agent'] = ''
-      headers['user-agent'] += self.user_agent
+        headers['user-agent'] =  self.user_agent
       return request_orig(uri, method, body, headers,
                           redirections, connection_type)
 
diff --git a/httplib2/__init__.py b/httplib2/__init__.py
index 61e9caa..567e24e 100644
--- a/httplib2/__init__.py
+++ b/httplib2/__init__.py
@@ -55,9 +55,9 @@
 import socket
 
 try:
-  from httplib2 import socks
+    from httplib2 import socks
 except ImportError:
-  socks = None
+    socks = None
 
 # Build the appropriate socket wrapper for ssl
 try:
@@ -83,7 +83,7 @@
 __all__ = ['Http', 'Response', 'ProxyInfo', 'HttpLib2Error',
   'RedirectMissingLocation', 'RedirectLimit', 'FailedToDecompressContent',
   'UnimplementedDigestAuthOptionError', 'UnimplementedHmacDigestAuthOptionError',
-  'debuglevel']
+  'debuglevel', 'ProxiesUnavailableError']
 
 
 # The httplib debug level, set to a non-zero value to get debug output
@@ -125,6 +125,7 @@
 
 class RelativeURIError(HttpLib2Error): pass
 class ServerNotFoundError(HttpLib2Error): pass
+class ProxiesUnavailableError(HttpLib2Error): pass
 
 # Open Items:
 # -----------
@@ -721,6 +722,9 @@
     def connect(self):
         """Connect to the host and port specified in __init__."""
         # Mostly verbatim from httplib.py.
+        if self.proxy_info and socks is None:
+            raise ProxiesUnavailableError(
+                'Proxy support missing but proxy use was requested!')
         msg = "getaddrinfo returns an empty list"
         for res in socket.getaddrinfo(self.host, self.port, 0,
                 socket.SOCK_STREAM):
diff --git a/httplib2/socks.py b/httplib2/socks.py
index 6f4f020..b65fb38 100644
--- a/httplib2/socks.py
+++ b/httplib2/socks.py
@@ -41,12 +41,13 @@
 """
 
 import socket
+
+if getattr(socket, 'socket', None) is None:
+    raise ImportError('socket.socket missing, proxy support unusable')
+
 import struct
 import sys
 
-if not hasattr(socket, 'socket'):
-  raise ImportError("Running on App Engine?")
-
 PROXY_TYPE_SOCKS4 = 1
 PROXY_TYPE_SOCKS5 = 2
 PROXY_TYPE_HTTP = 3