Weboob: NotImplementedError not caught in the weboob script

Trying the Nightly image, I've seen the synchronization stopped working for me, with the following error message:

Traceback (most recent call last):
  File "/home/user/app/build/server/weboob/main.py", line 450, in fetch
    results['values'].extend(fetch_function(backend))
  File "/home/user/app/build/server/weboob/main.py", line 384, in get_operations
    for line in history:
  File "/home/user/data/weboob-data/modules/1.4/creditmutuel/module.py", line 69, in iter_history
    for tr in self.browser.get_history(account):
  File "/weboob/weboob/browser/browsers.py", line 768, in inner
    return func(browser, *args, **kwargs)
  File "/home/user/data/weboob-data/modules/1.4/creditmutuel/browser.py", line 253, in get_history
    raise NotImplementedError()
NotImplementedError

Before, we caught it, but it seems it's not the case anymore. Could we handle that better to not stop the script at all? (cc @phyks)