HyperArch.py throws IndexError: string index out of range

[Mark Sapiro]

There is code in Mailman/Archiver/HyperArch.py which gets the character set of a message in order to convert it if necessary to the character set of the archive. The code is

        charset = message.get_content_charset(cset_out)
        if charset:
            charset = charset.lower().strip()
            if charset[0]=='"' and charset[-1]=='"':
                charset = charset[1:-1]
            if charset[0]=="'" and charset[-1]=="'":
                charset = charset[1:-1]

This code can throw an IndexError if get_content_charset() returns a non-null string containing only white space, e.g. a single new-line. It has been reported that this occurs resulting in tracebacks which end with something like

  File "Mailman/Archiver/HyperArch.py", line 311, in __init__
    if charset[0]=='"' and charset[-1]=='"':
IndexError: string index out of range

The obvious, 'simple' fix for this is to change

        if charset:

to

        if charset and charset.strip():

which will avoid the exception, but I really want to see an actual message that triggers this error as a test case for this and future changes.

Unfortunately, despite trying with multiple versions of the Python email package, the only way I can get get_content_charset() to return a whitespace only result is with a header like

Content-Type: text/plain; charset=" "

which seems a bit too contrived to actually occur in the wild.

Thus, if anyone can provide an actual message that triggers this exception, please attach it here.