Work around httplib2 tunnelling bug

Fixes bug #1051007

httplib2 defaults to using HTTP CONNECT tunnelling even for plain HTTP
connections. This is problematic with proxies configured to only allow
tunnelling to port 443. This is the default configuration for squid.

Hack around the problem by forcing httplib2 to use the HTTP_NO_TUNNEL
proxy type which disables tunnelling except for port 443.

Change-Id: I59cd95ed74a9bb795779fc38fbc0935266cc8b22

novaclient/client.py

@@ -46,6 +46,37 @@ def get_auth_system_url(auth_system):
     raise exceptions.AuthSystemNotFound(auth_system)
 
 
+def _get_proxy_info():
+    """Work around httplib2 proxying bug.
+
+    Full details of the bug here:
+
+      http://code.google.com/p/httplib2/issues/detail?id=228
+
+    Basically, in the case of plain old http with httplib2>=0.7.5 we
+    want to ensure that PROXY_TYPE_HTTP_NO_TUNNEL is used.
+    """
+    def get_proxy_info(method):
+        pi = httplib2.ProxyInfo.from_environment(method)
+        if pi is None or method != 'http':
+            return pi
+
+        # We can't rely on httplib2.socks being available
+        # PROXY_TYPE_HTTP_NO_TUNNEL was introduced in 0.7.5
+        if not (hasattr(httplib2, 'socks') and
+                hasattr(httplib2.socks, 'PROXY_TYPE_HTTP_NO_TUNNEL')):
+            return pi
+
+        pi.proxy_type = httplib2.socks.PROXY_TYPE_HTTP_NO_TUNNEL
+        return pi
+
+    # 0.7.3 introduced configuring proxy from the environment
+    if not hasattr(httplib2.ProxyInfo, 'from_environment'):
+        return None
+
+    return get_proxy_info
+
+
 class HTTPClient(httplib2.Http):
 
     USER_AGENT = 'python-novaclient'
@@ -57,7 +88,8 @@ def __init__(self, user, password, projectid, auth_url=None,
                  service_name=None, volume_service_name=None,
                  timings=False, bypass_url=None, no_cache=False,
                  http_log_debug=False, auth_system='keystone'):
-        super(HTTPClient, self).__init__(timeout=timeout)
+        super(HTTPClient, self).__init__(timeout=timeout,
+                                         proxy_info=_get_proxy_info())
         self.user = user
         self.password = password
         self.projectid = projectid