handle Exception and remove duplication in errors.py

ensure that if unexpected Exceptions are thrown, we handle them correctly
(log and then return JSON)

also remove some branches that will never trip, and combine a couple of
identical functions

app/errors.py

@@ -42,10 +42,7 @@ def register_errors(blueprint):
 
     @blueprint.app_errorhandler(400)
     def bad_request(e):
-        if isinstance(e, str):
-            msg = e
-        else:
-            msg = e.description or "Invalid request parameters"
+        msg = e.description or "Invalid request parameters"
         current_app.logger.exception(msg)
         return jsonify(result='error', message=str(msg)), 400
 
@@ -61,10 +58,7 @@ def register_errors(blueprint):
 
     @blueprint.app_errorhandler(404)
     def page_not_found(e):
-        if isinstance(e, str):
-            msg = e
-        else:
-            msg = e.description or "Not found"
+        msg = e.description or "Not found"
         current_app.logger.exception(msg)
         return jsonify(result='error', message=msg), 404
 
@@ -73,18 +67,9 @@ def register_errors(blueprint):
         current_app.logger.exception(e)
         return jsonify(result='error', message=str(e.description)), 429
 
-    @blueprint.app_errorhandler(500)
-    def internal_server_error(e):
-        current_app.logger.exception(e)
-        return jsonify(result='error', message="Internal server error"), 500
-
     @blueprint.app_errorhandler(NoResultFound)
-    def no_result_found(e):
-        current_app.logger.exception(e)
-        return jsonify(result='error', message="No result found"), 404
-
     @blueprint.app_errorhandler(DataError)
-    def data_error(e):
+    def no_result_found(e):
         current_app.logger.exception(e)
         return jsonify(result='error', message="No result found"), 404
 
@@ -101,3 +86,10 @@ def register_errors(blueprint):
                 )]}
             ), 400
         return jsonify(result='error', message="Internal server error"), 500
+
+    # this must be defined after all other error handlers since it catches the generic Exception object
+    @blueprint.app_errorhandler(500)
+    @blueprint.app_errorhandler(Exception)
+    def internal_server_error(e):
+        current_app.logger.exception(e)
+        return jsonify(result='error', message="Internal server error"), 500