exceptions: fixed .message deprecated in python3

vcsserver/http_main.py

@@ -653,11 +653,11 b' class HTTPApplication(object):'
             # Get custom repo-locked status code if present.
             status_code = request.headers.get('X-RC-Locked-Status-Code')
             return HTTPRepoLocked(
-                title=exception.message, status_code=status_code)
+                title=str(exception), status_code=status_code)
 
         elif _vcs_kind == 'repo_branch_protected':
             # Get custom repo-branch-protected status code if present.
-            return HTTPRepoBranchProtected(title=exception.message)
+            return HTTPRepoBranchProtected(title=str(exception))
 
         exc_info = request.exc_info
         store_exception(id(exc_info), exc_info)