race condition between multiple calls of add_additional_packages and/or remove_additional_packages

Originally created by @alant on #15982 (Redmine)

if the config file is written between when the packages are read and when the packages are written, this change will be overwritten by the subsequent write. You could fix this by acquiring a file lock before reading the file, for example with fcntl.flock(f, fcntl.LOCK_EX), and only releasing the lock once the file was written (example: https://gitlab.com/segfault3/onionkit/blob/master/onionkit/util.py#L21).
This way you could also get rid of the python3-atomicwrites package

Parent Task: #15838 (closed)

Related issues

• Has duplicate #16034