Fix mongodb user compatibility check (#2731)

- Check the compatibility asap

database/misc/mongodb_user.py

@@ -174,13 +174,26 @@ else:
 #
 
 def check_compatibility(module, client):
-    srv_info = client.server_info()
-    if LooseVersion(srv_info['version']) >= LooseVersion('3.2') and LooseVersion(PyMongoVersion) <= LooseVersion('3.2'):
+    """Check the compatibility between the driver and the database.
+
+       See: https://docs.mongodb.com/ecosystem/drivers/driver-compatibility-reference/#python-driver-compatibility
+
+    Args:
+        module: Ansible module.
+        client (cursor): Mongodb cursor on admin database.
+    """
+    loose_srv_version = LooseVersion(client.server_info()['version'])
+    loose_driver_version = LooseVersion(PyMongoVersion)
+
+    if loose_srv_version >= LooseVersion('3.2') and loose_driver_version <= LooseVersion('3.2'):
         module.fail_json(msg=' (Note: you must use pymongo 3.2+ with MongoDB >= 3.2)')
-    elif LooseVersion(srv_info['version']) >= LooseVersion('3.0') and LooseVersion(PyMongoVersion) <= LooseVersion('2.8'):
+
+    elif loose_srv_version >= LooseVersion('3.0') and loose_driver_version <= LooseVersion('2.8'):
         module.fail_json(msg=' (Note: you must use pymongo 2.8+ with MongoDB 3.0)')
-    elif LooseVersion(srv_info['version']) >= LooseVersion('2.6') and LooseVersion(PyMongoVersion) <= LooseVersion('2.7'):
+
+    elif loose_srv_version >= LooseVersion('2.6') and loose_srv_version <= LooseVersion('2.7'):
         module.fail_json(msg=' (Note: you must use pymongo 2.7+ with MongoDB 2.6)')
+
     elif LooseVersion(PyMongoVersion) <= LooseVersion('2.5'):
         module.fail_json(msg=' (Note: you must be on mongodb 2.4+ and pymongo 2.5+ to use the roles param)')
 
@@ -339,6 +352,10 @@ def main():
 
         client = MongoClient(**connection_params)
 
+        # NOTE: this check must be done ASAP.
+        # We doesn't need to be authenticated.
+        check_compatibility(module, client)
+
         if login_user is None and login_password is None:
             mongocnf_creds = load_mongocnf()
             if mongocnf_creds is not False:
@@ -357,8 +374,6 @@ def main():
     except Exception, e:
         module.fail_json(msg='unable to connect to database: %s' % str(e))
 
-    check_compatibility(module, client)
-
     if state == 'present':
         if password is None and update_password == 'always':
             module.fail_json(msg='password parameter required when adding a user unless update_password is set to on_create')