The tool `add-apt-repository` does require the package `gnupg` to work
correctly. I tested this by running a Debian container using
Docker, installing `software-properties-common` and trying to use
`add-apt-repository`. I tried to add the repository
`ppa:andreasbutti/xournalpp-master`.

In addition, `add-apt-repository` does not exit with an exit code
unequal to 0 while raising an exception, this can be seen at the end of
the recording.

The error was:
```
Exception in thread Thread-1:
Traceback (most recent call last):
  File "/usr/lib/python3.8/threading.py", line 932, in _bootstrap_inner
    self.run()
  File "/usr/lib/python3.8/threading.py", line 870, in run
    self._target(*self._args, **self._kwargs)
  File "/usr/lib/python3/dist-packages/softwareproperties/SoftwareProperties.py", line 688, in addkey_func
    func(**kwargs)
  File "/usr/lib/python3/dist-packages/softwareproperties/ppa.py", line 386, in add_key
    return apsk.add_ppa_signing_key()
  File "/usr/lib/python3/dist-packages/softwareproperties/ppa.py", line 251, in add_ppa_signing_key
    if not self._recv_key(
  File "/usr/lib/python3/dist-packages/softwareproperties/ppa.py", line 176, in _recv_key
    res = subprocess.call(self.GPG_DEFAULT_OPTIONS + [
  File "/usr/lib/python3.8/subprocess.py", line 340, in call
    with Popen(*popenargs, **kwargs) as p:
  File "/usr/lib/python3.8/subprocess.py", line 854, in __init__
    self._execute_child(args, executable, preexec_fn, close_fds,
  File "/usr/lib/python3.8/subprocess.py", line 1702, in _execute_child
    raise child_exception_type(errno_num, err_msg, err_filename)
FileNotFoundError: [Errno 2] No such file or directory: 'gpg'
```

I recorded a shell session with asciinema to allow you insight in how I
tested this. The recording is attached to this bug report, but this
recording can also be watched here: https://asciinema.org/a/HGoNlw5HuvoRnnQxecDmFqxSd

Hi,

please find attached a patch. If Julian or nobody else objects or jumps
in, I can NMU in about one week.

Cheers,
Bruno

Control: severity -1 normal
old version that actually needs key server functionality (dirmngr and
gnupg), and I absolutely do not want to depend on those.

I also don't think this is a release critical bug - the script is not
the main attraction, it does not produce immediate useful results on
Debian anyway if you add a PPA, given that the PPAs do not exist for
Debian in the first place, and other uses do not involve that codepath
AFAIUI.

Anyhow, this email was the first time I heard about this bug, and it did
not provide any context (and I can't open attachments on my phone), so I
was a bit unhappy, and I did not have a lot of time to dig into it yet.

My advise for future NMU emails: Please keep the original bug subject in
the subject, and quote the bug report so readers can make sense out of
it without having to search for the bug in the BTS.

We really ought to update software-properties to the Ubuntu 20.04
version rather than try to ship the 16.04 one - it's 5 years old by now.
I have no idea what happened here that we're still on the old version, I
did upload the 18.04 one to experimental 2 years ago.

This also fixes this bug because it now talks to the keyserver directly,
and drops the file into trusted.gpg.d.

Generally, please: If I have not answered you for a month, your email
was lost, if it's still a problem, please ping me.

Am Sonntag, dem 24.01.2021 um 10:38 +0100 schrieb Julian Andres Klode:

Hi Julian,

my apologies for the inconveniences. I must admit, I'm not a user of
the script and didn't test it with and without the dependency. I only
convinced myself that gpg is called and assumed the missing dependency
is valid.

I realize I don't understand enough of the package to fix anything by
simply adding gpg to the dependency list and won't NMU.

Cheers,
Bruno