Merge branch 'p1' into 'master'

Fix pubkey extraction on update

Replacement of !86.

Fix pubkey extraction in case of non-empty _JAVA_OPTIONS. Fixes #133.

I didn't actually run the test suite (it looks like there are some preparations to be done for that), but I checked the commands from `test_fdroid_popen_stderr_redirect` in ipython.

See merge request !103

diff --cc fdroidserver/common.py
Simple merge

diff --cc fdroidserver/update.py
Simple merge