Fix from_response method to process response from requests

SessionClient uses requests library. It's response class doesn't have
"status" property[1], so in case of any errors(with status code > 400),
from_response method is called and raises AttributeError.

Also, HTTPClient implementation uses requests lib by default[2](if 'http'
argument was not transmitted), so from_response method will raise
AttributeError too.

[1] - http://docs.python-requests.org/en/master/api/#requests.Response.status_code
[2] - https://github.com/openstack/python-ceilometerclient/blob/2.6.0/ceilometerclient/openstack/common/apiclient/client.py#L99-L100

Change-Id: Id8fb2f386e8101951716f30a6365c9aa15bd4b24
Closes-Bug: #1620974
(cherry picked from commit 1b1917ab9b)

ceilometerclient/exc.py

@@ -118,6 +118,16 @@ for obj_name in dir(sys.modules[__name__]):
 
 
 def from_response(response, details=None):
-    """Return an instance of an HTTPException based on httplib response."""
-    cls = _code_map.get(response.status, HTTPException)
+    """Return an instance of an HTTPException based on http response."""
+    if hasattr(response, "status"):
+        # it is response from HTTPClient (httplib)
+        code = response.status
+    elif hasattr(response, "status_code"):
+        # it is response from SessionClient (requests)
+        code = response.status_code
+    else:
+        # it is something unexpected
+        raise TypeError("Function 'from_response' expects only response object"
+                        " from httplib or requests libraries.")
+    cls = _code_map.get(code, HTTPException)
     return cls(details)

ceilometerclient/tests/unit/test_exc.py

@@ -69,3 +69,19 @@ class HTTPExceptionsTest(utils.BaseTestCase):
                 {"error_message": {"faultstring": "oops"}}))
             ret_str = k + " (HTTP " + str(exception.code) + ") ERROR oops"
             self.assertEqual(ret_str, str(exception))
+
+    def test_from_response(self):
+        class HTTPLibLikeResponse(object):
+            status = 400
+
+        class RequestsLikeResponse(object):
+            status_code = 401
+
+        class UnexpectedResponse(object):
+            code = 200
+
+        self.assertEqual(HTTPLibLikeResponse.status,
+                         exc.from_response(HTTPLibLikeResponse).code)
+        self.assertEqual(RequestsLikeResponse.status_code,
+                         exc.from_response(RequestsLikeResponse).code)
+        self.assertRaises(TypeError, exc.from_response, UnexpectedResponse)