client: Define HTTP{,S}Connection class to use as class attributes.

So they can be customised in subclasses.

caucase/client.py

@@ -51,6 +51,8 @@ class CaucaseClient(object):
 
   Expose caucase REST API as pythonic methods.
   """
+  HTTPConnection = httplib.HTTPConnection
+  HTTPSConnection = httplib.HTTPSConnection
 
   @classmethod
   def updateCAFile(cls, url, ca_crt_path):
@@ -120,7 +122,7 @@ class CaucaseClient(object):
     # XXX: set timeout to HTTP connections ?
     http_url = urlparse(ca_url)
     port = http_url.port or 80
-    self._http_connection = httplib.HTTPConnection(
+    self._http_connection = self.HTTPConnection(
       http_url.hostname,
       port,
       #timeout=,
@@ -138,7 +140,7 @@ class CaucaseClient(object):
           ssl_context.load_cert_chain(user_key)
         except ssl.SSLError as exc:
           raise ValueError('Failed to load user key: %r' % (exc, ))
-      self._https_connection = httplib.HTTPSConnection(
+      self._https_connection = self.HTTPSConnection(
         http_url.hostname,
         443 if port == 80 else port + 1,
         #timeout=,