First `yarn devserver` on new KOLIBRI_HOME fails first time only

Observed behavior

I’ve seen this before and thought it was to do with me getting crazy with changing my KOLIBRI_HOME and branches because I used to just run all of my pip and yarn installs then retry starting the dev server - but now that I’ve seen it a few times I figure I should make an issue - especially after it just worked without me doing all of that reinstalling of dependencies.

1. Set your KOLIBRI_HOME to a non-existent folder
2. yarn devserver
3. See that it fails:

Traceback (most recent call last):
  File "/home/jacob/.pyenv/versions/3.7.7/bin/kolibri", line 11, in <module>
    load_entry_point('kolibri', 'console_scripts', 'kolibri')()
  File "/home/jacob/.pyenv/versions/3.7.7/lib/python3.7/site-packages/pkg_resources/__init__.py", line 489, in load_entry_point
    return get_distribution(dist).load_entry_point(group, name)
  File "/home/jacob/.pyenv/versions/3.7.7/lib/python3.7/site-packages/pkg_resources/__init__.py", line 2843, in load_entry_point
    return ep.load()
  File "/home/jacob/.pyenv/versions/3.7.7/lib/python3.7/site-packages/pkg_resources/__init__.py", line 2434, in load
    return self.resolve()
  File "/home/jacob/.pyenv/versions/3.7.7/lib/python3.7/site-packages/pkg_resources/__init__.py", line 2440, in resolve
    module = __import__(self.module_name, fromlist=['__name__'], level=0)
  File "/home/jacob/Code/LearningEquality/kolibri/kolibri/utils/cli.py", line 29, in <module>
    from . import sanity_checks
  File "/home/jacob/Code/LearningEquality/kolibri/kolibri/utils/sanity_checks.py", line 10, in <module>
    from .conf import KOLIBRI_HOME
  File "/home/jacob/Code/LearningEquality/kolibri/kolibri/utils/conf.py", line 42, in <module>
    os.mkdir(KOLIBRI_HOME)
FileExistsError: [Errno 17] File exists: '/media/hdd/kolibris/14-informal'

1. yarn devserver - now it works as expected.

Looks like the new home folder is being made twice without something catching the error when it tries and fails after it first finds that the folder doesn’t exist yet?

Expected behavior

I make a new KOLIBRI_HOME and can start the devserver on the first try.

User-facing consequences

Confusing for developers and contributors.

Context

0.14-beta9 Debian 10 Chrome

[rtibbles]

I am fairly sure that this would be fixed by #7254 - where for the devserver we use the production kolibri server running in autoreload mode. We already have safeguards against a non-existent Kolibri home in our production environment, so this would give a parallel experience for devs.

[jonboiser]

Fixed in #7938, specifically for the non-existent KOLIBRI_HOME folder case.