MR: add (un)subscribe support

gitlab/objects.py

@@ -1099,7 +1099,7 @@ def unsubscribe(self, **kwargs):
 
         Raises:
             GitlabConnectionError: If the server cannot be reached.
-            GitlabSubscribeError: If the unsubscription cannot be done
+            GitlabUnsubscribeError: If the unsubscription cannot be done
         """
         url = ('/projects/%(project_id)s/issues/%(issue_id)s/subscription' %
                {'project_id': self.project_id, 'issue_id': self.id})
@@ -1249,6 +1249,36 @@ def _data_for_gitlab(self, extra_parameters={}, update=False):
             data = json.dumps(d)
         return data
 
+    def subscribe(self, **kwargs):
+        """Subscribe to a MR.
+
+        Raises:
+            GitlabConnectionError: If the server cannot be reached.
+            GitlabSubscribeError: If the subscription cannot be done
+        """
+        url = ('/projects/%(project_id)s/merge_requests/%(mr_id)s/'
+               'subscription' %
+               {'project_id': self.project_id, 'mr_id': self.id})
+
+        r = self.gitlab._raw_post(url, **kwargs)
+        raise_error_from_response(r, GitlabSubscribeError, [201, 304])
+        self._set_from_dict(r.json())
+
+    def unsubscribe(self, **kwargs):
+        """Unsubscribe a MR.
+
+        Raises:
+            GitlabConnectionError: If the server cannot be reached.
+            GitlabUnsubscribeError: If the unsubscription cannot be done
+        """
+        url = ('/projects/%(project_id)s/merge_requests/%(mr_id)s/'
+               'subscription' %
+               {'project_id': self.project_id, 'mr_id': self.id})
+
+        r = self.gitlab._raw_delete(url, **kwargs)
+        raise_error_from_response(r, GitlabUnsubscribeError, [200, 304])
+        self._set_from_dict(r.json())
+
     def cancel_merge_when_build_succeeds(self, **kwargs):
         """Cancel merge when build succeeds."""
 
@@ -1377,7 +1407,7 @@ def unsubscribe(self, **kwargs):
 
         Raises:
             GitlabConnectionError: If the server cannot be reached.
-            GitlabSubscribeError: If the unsubscription cannot be done
+            GitlabUnsubscribeError: If the unsubscription cannot be done
         """
         url = ('/projects/%(project_id)s/labels/%(label_id)s/subscription' %
                {'project_id': self.project_id, 'label_id': self.name})