Fix expanding not working when running in a server

requests_mocker bug which makes requests parameters case insensitive needs a flag until a major version release.

Author: davidweterings

src/commercetools/testing/__init__.py

@@ -113,7 +113,7 @@ def register(self, adapter):
 
 @contextmanager
 def backend_mocker(*args, **kwargs):
-    with requests_mock.Mocker(real_http=True) as m:
+    with requests_mock.Mocker(real_http=True, case_sensitive=True) as m:
         repo = BackendRepository()
         repo.register(m)
         yield repo

src/commercetools/testing/server.py

@@ -39,7 +39,7 @@ def __init__(self, repository=None):
 
     def __call__(self, environ, start_response):
         request = self._create_request(environ)
-        request_mock = _RequestObjectProxy(request.prepare())
+        request_mock = _RequestObjectProxy(request.prepare(), case_sensitive=True)
 
         if request_mock.body is None:
             request_mock.body = ""