Add support for handling double posting of same user.

Fix non-json test to make builds green.

api/rookeries/errors.py

@@ -33,6 +33,11 @@ class InvalidOperationError(Exception):
         self.message = message
 
 
+class ConflictingResourceError(Exception):
+    def __init__(self, message=http.HTTPStatus.CONFLICT.description):
+        self.message = message
+
+
 def get_message_for_status(http_code):
     try:
         http_status = http.HTTPStatus(http_code)
@@ -76,6 +81,19 @@ def error_message_from_invalid_op_error(error: InvalidOperationError):
     return flask.jsonify(error_message), http.HTTPStatus.FORBIDDEN
 
 
+def error_message_from_conflicting_resource_error(error: ConflictingResourceError):
+    logger.error(f'Conflicting resource for "{flask.request.url}" because "{error.message}"')
+    error_message = {
+        'error': {
+            'status_code': http.HTTPStatus.CONFLICT,
+            'message': f'{error.message}',
+            'resource': flask.request.url,
+        }
+    }
+
+    return flask.jsonify(error_message), http.HTTPStatus.CONFLICT
+
+
 def error_message_from_exception(error: Exception):
     logger.exception(f'Uncaught error while processing "{flask.request.url}":')
     error_message = {
@@ -106,5 +124,6 @@ def attach_error_handlers_to_api_app(app):
         app.register_error_handler(http_code, error_message_from_http_code)
 
     app.register_error_handler(InvalidOperationError, error_message_from_invalid_op_error)
+    app.register_error_handler(ConflictingResourceError, error_message_from_conflicting_resource_error)
     app.register_error_handler(jsonschema.ValidationError, error_message_from_json_schema_validation_error)
     app.register_error_handler(Exception, error_message_from_exception)

api/rookeries/users/views.py

@@ -60,7 +60,10 @@ def create_user():
     if requesting_user_role != models.UserRole.admin:
         flask.abort(http.HTTPStatus.UNAUTHORIZED)
 
-    # Creates a user from the json.
+    # Creates a user from the json if no user exists with the given username.
+    if models.User.query.filter_by(username=incoming_request['username']).first():
+        raise errors.ConflictingResourceError('Existing resource already found.  PUT to the resource to update it.')
+
     user = models.User.from_json(incoming_request)
     db.session.add(user)
     db.session.commit()

api/tests/server/test_user_management.py

@@ -171,11 +171,11 @@ def modify_non_existent_user_response(requester, api_base_uri):
     )
 
 
-@bdd.given(parsers.parse('I try to create an user with a non-JSON request'), target_fixture='user_response')
+@bdd.given(parsers.parse('I try to create an user with a non-json request'), target_fixture='user_response')
 def invalid_non_json_create_new_user_response(requester, api_base_uri):
     return requests.post(
         url=f'{api_base_uri}/api/users',
-        body='',
+        data='',
         headers={
             'Authorization': f'JWT {requester.token}',
         },
@@ -193,11 +193,11 @@ def invalid_empty_create_new_user_response(requester, api_base_uri):
     )
 
 
-@bdd.given(parsers.parse('I try to modify an user with a non-JSON request'), target_fixture='user_response')
+@bdd.given(parsers.parse('I try to modify an user with a non-json request'), target_fixture='user_response')
 def invalid_non_json_modify_user_response(requester, api_base_uri):
     return requests.put(
         url=f'{api_base_uri}/api/users/test_user',
-        body='',
+        data='',
         headers={
             'Authorization': f'JWT {requester.token}',
         },