The operator's description used a format string like:
```
BLI_sprintfN(TIP_("%s %s vertex groups of the active object"),
action_str, target_str)
```
which is almost guaranteed to be impossible to properly localize to
some languages -- I know there are a couple of issues for French
already.
So instead of hoping formatting works, write all possible strings
explicitly, even if it looks stupidly verbose.
Damien Picard