Only call super() during MockHttp if required

With pytest 8.2 and above, any class that contains classes is collected,
which means they are instantiated, which MockHttp's superclasses do not
accept, since they require keyword arguments. To work around this, only
call the superclass's __init__ method if we are passed kwargs.

libcloud/test/__init__.py

@@ -87,7 +87,7 @@ def read(self, chunk_size=None):
         return StringIO.read(self)
 
 
-class MockHttp(LibcloudConnection):
+class MockHttp(LibcloudConnection, unittest.TestCase):
     """
     A mock HTTP client/server suitable for testing purposes. This replaces
     `HTTPConnection` by implementing its API and returning a mock response.
@@ -108,7 +108,11 @@ def __init__(self, *args, **kwargs):
         # within a response
         if isinstance(self, unittest.TestCase):
             unittest.TestCase.__init__(self, "__init__")
-        super().__init__(*args, **kwargs)
+        # When this class is collected, it is instantiated with no arguments,
+        # which breaks any superclasses that expect arguments, so only
+        # do so if we were passed any keyword arguments.
+        if kwargs:
+            super().__init__(*args, **kwargs)
 
     def _get_request(self, method, url, body=None, headers=None):
         # Find a method we can use for this request