BUG: api session: better error message with disabled session storage

the error message when the session storage was disabled was misleading
as it suggested wrong credentials, but actually no login is required and
possible.

the intelmq-manager shows a fixed error message and needs a fix as well

CHANGELOG.rst

@@ -8,7 +8,7 @@ CHANGELOG
 
 3.0.1 (unreleased)
 ------------------
-
+- Return a matching error message if the session storage is disabled and therefore a login is not possible (PR#36 by Sebastian Wagner, fixes #35).
 
 3.0.0 (2021-07-07)
 ------------------

intelmq_api/api.py

@@ -185,14 +185,17 @@ def config(response, file: str, fetch: bool=False):
 
 @hug.post("/api/login", versions=1)
 def login(username: str, password: str):
-    if session_store is not None:
+    if session_store is None:
+        return {"error": "Session store is disabled by configuration! No login possible and required."}
+    else:
         known = session_store.verify_user(username, password)
         if known is not None:
             token = session_store.new_session({"username": username})
             return {"login_token": token,
                     "username": username,
                     }
-    return "Invalid username and/or password"
+        else:
+            return {"error": "Invalid username and/or password."}
 
 
 @hug.get("/api/harmonization", requires=token_authentication, versions=1)