Corrected Google Cloud VM error: (#125)

On Google Cloud VMs, the user's account email is stored in a different
attribute of the Session's Credentials object (service_account_email
rather than id_token). The existence of the attributes are also mutually
exclusive. This caused an AttributeError when accessing a non-existent
attribute, and failure to populate __USER_ID, which broke several
functions. Updated api.py to handle the different attribute locations.

changelog.txt

@@ -3,6 +3,10 @@ Change Log for FISSFC: the (Fi)recloud (S)ervice (S)elector
 =======================================================================
 Terms used below:  HL = high level interface, LL = low level interface
 
+v0.16.24 - Hotfix: corrected error in api.py due to difference in user ID
+           location when run from a Google Cloud VM; setup.py updated to
+           explicitly designate long_description_content_type as text/plain.
+
 v0.16.23 - LL: get_entities_tsv updated with ability to specify ordered
            attributes and data model, upload_entities and upload_entities_tsv
            updated to enable use of flexible data model API; HL: added back

firecloud/__about__.py

@@ -1,2 +1,2 @@
 # Package version
-__version__ = "0.16.23"
+__version__ = "0.16.24"

firecloud/api.py

@@ -52,6 +52,8 @@ def _set_session():
             health()
             __USER_ID = id_token.verify_oauth2_token(__SESSION.credentials.id_token,
                                                      Request(session=__SESSION))['email']
+        except AttributeError:
+            __USER_ID = __SESSION.credentials.service_account_email
         except (DefaultCredentialsError, RefreshError) as gae:
             if os.getenv('SERVER_SOFTWARE', '').startswith('Google App Engine/'):
                 raise