Bump pyxdg from 0.25 to 0.26

Bumps [pyxdg](https://github.com/takluyver/pyxdg) from 0.25 to 0.26. - [Release notes](https://github.com/takluyver/pyxdg/releases) - [Changelog](https://github.com/takluyver/pyxdg/blob/master/ChangeLog) - [Commits](takluyver/pyxdg@rel-0.25...rel-0.26) Signed-off-by: dependabot[bot] <support@github.com>

Author: dependabot[bot]

requirements.txt

@@ -35,7 +35,7 @@ pyRFC3339==1.0
 python-debian==0.1.32
 python-xlib==0.26
 pytz==2019.3
-pyxdg==0.25
+pyxdg==0.26
 PyYAML==3.12
 reportlab==3.4.0
 requests==2.18.4