Add request to Custom Script run, if receiver supports it

[steffann]

Fixes: #3705

• Check whether the script.run() method accepts request as a keyword argument
• If it does, pass the current request to the method

[steffann]

I implemented this as a keyword-only option to prevent any clashes with existing scripts that already have a run() method with multiple arguments. It's impossible to know how users have implemented their current scripts, better be safe than sorry…

[jeremystretch]

Rather than altering the signature of run(), my plan was to make the current request available as a context in the Script object. For example, the script author would access self.request.user to get the current user (if any). This avoids the need to adapt existing scripts, and allows for cleanly running scripts without a request present (e.g. when executed locally via cron job).

[steffann]

No problem, I considered both approaches but wasn't sure what the lifetime of a Script object was, and I didn't want to keep a long-lived reference to the request hanging around in a property. If that's not a problem then I agree your approach is cleaner.

I'll adapt the implementation!

[jeremystretch]

@steffann Can you re-base this against the develop branch please? I don't think there's any reason to wait for v2.7 as it won't be a disruptive change.

[steffann]

Done. In the end I just reset to develop and cherry-picked the patch.