provision: Do not even suggest the --force option.

Suggesting to users that they use '--force' during provision
is just asking for trouble.  We will probably want to deprecate
that altogether soon.

tools/provision

@@ -40,7 +40,7 @@ the Python version this command is executed with."""
 
     if py_version <= (3, 1) and (not options.force):
         print(red + "Provision failed: Cannot create venv with outdated Python version ({}).\n"
-              "Run this script with --force if you want to proceed anyway."
+              "Maybe try `python3 tools/provision`."
               .format(py_version_output.strip()) + end_format)
         sys.exit(1)