[Owncloud] How to debug an HTTP 400 error from Owncloud?

[Chris Green]

I'm running a program called pycardsyncer (part of the pycarddav
package) to upload new contacts to the Owncloud contacts app.

I did have it working very nicely but then I changed some python
packages and I can't get it working again.  I have tried as far as I can
to get back to the original set-up but so far I've failed to find the
problem.

The program (pycardsyncer) can download Vcards from Owncloud OK, it's
only when it tries to upload a new Vcard that I get the error.  The
error that pycardsyncer reports is:-

    requests.exceptions.HTTPError: 400 Client Error

The PUT that gets the error is:-

    PUT /owncloud/remote.php/carddav/addressbooks/chris/contacts/67FE609A-B7CB1471-6D9EBF5F.vcf ('HTTP/1.1',)"


The trouble is I can't find any logging anywhere that gives me any sort
of reason for the HTTP 400 error.  I have looked in the apache2 error.log on
my server and there's nothing there, there's nothing in the Owncloud
logs and nothing anywhere else I can think of.


Can someone suggest how I might diagnose this further?

-- 
Chris Green