Building docs fails with Sphinx 7.2 and SOURCE_DATE_EPOCH environment variable

[s3v-]

Hi,
Currently your package fails to build from source in Debian with Sphinx 7.2:
https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=1042693
The failure is caused by SOURCE_DATE_EPOCH environment variable added during build in Debian.
Please see here and here for reference.

Step to reproduce:

$ export SOURCE_DATE_EPOCH=1699613320; sphinx-build -b html python-django-celery-results-2.5.1/docs/ .

Running Sphinx v7.2.6
WARNING: html_static_path entry '_static' is placed inside outdir

Extension error (sphinx.config):
Handler <function correct_copyright_year at 0x7f6891a0cae0> for event 'config-inited' threw an exception (exception: string index out of range)

Offending line:

django-celery-results/docs/conf.py

Line 13 in cb94489

copyright='2009-2022',

This change solves the issue:

copyright='2009-2022, something',

Kind Regards