I need some help interpreting this error

[2QdxY4RzWzUUiLuE at potatochowder.com]

On 2021-02-17 at 17:36:48 +0000,
Chris Green <cl at isbd.net> wrote:

> Stefan Ram <ram at zedat.fu-berlin.de> wrote:
> > Chris Green <cl at isbd.net> writes:
> > >    chris at cheddar$ tail mail.err
> > >    Traceback (most recent call last):
> > >      File "/home/chris/.mutt/bin/filter.py", line 95, in <module>
> > >        if sbstrip in msghdr["subject"]:
> > >    TypeError: argument of type 'Header' is not iterable
> > >But msghdr["subject"] is surely just a string isn't it?  Why is it 
> > >complaining about something of type 'Header'?
> > 
> >   I presume that the error message has been edited (abbreviated).
> > 
> >   In "if sbstrip in msghdr["subject"]:", there is no argument.
> > 
> >   But the error message says "argument of ...".
> > 
> >   When something that is not iterable is presented to a for loop,
> >   the error message does not mention "argument":
> > 
> I have output everything that appears, I've not changed it at all.
> It's the whole content of the file ~/tmp/mail.err as it's the only
> error that has occurred for the last day or so.  The error log is
> created by the line:-
> 
>     sys.stderr = open("/home/chris/tmp/mail.err", 'a')
> 
> So that's everything that was output to stderr.
> 
> I think you are puzzled in the same way that I was, the error message
> doesn't make a lot of sense.  

At some point, the internal code for the "in" operator is likely
iterating over the elements of msghdr["subject"].

That error message doesn't make a lot of sense if msghdr["subject"] is a
sub-class of str.  It makes more sense if msghdr["subject"] is something
else.

IMO, you need more information in the log, a try/except block to prevent
the code from crashing, and, yes, perhaps some patience to wait for it
to happen again.

Sometimes, developing software isn't all fortune, fame, and glory.  ;-)