Module Import Error with Nosetests and Tox - python-3.6

Question

In my project, I am using tox with nosetests. Using PyCharm, my tox pipeline was passing completely including all the tests. When I execute tox on a Ubuntu18.04 container with python3, it gives me the following error:
ImportError: No module named 'my_project'
leading to the following error at the end:
ERROR: InvocationError for command /.tox/py36/bin/nosetests (exited with code 1)
my_project is the name of the module I am testing and the directory structure looks like this under /, the root dir from which I am executing tox:
my_project/
tests/
tox.ini
setup.cfg
other files
My tox.ini looks as follows:
[tox]
envlist = py36
[testenv]
commands = python3 setup.py build
nosetests
deps = -r{toxinidir}/test-requirements.txt
I have tried to provide the path to project in different ways to nosetests command but none of that works. One line that interests me is in the initial output of tox:
py36 installed: my_project # file:///.tox/.tmp/package/1/my_project-0.4.post52.dev256143400.zip,
which leads me to think if this is the reason that nosetests does not find my_project.
For details, the stack trace for the error is as follows:
ERROR: Failure: ImportError (No module named 'my_project')
Traceback (most recent call last):
File "/.tox/py36/lib/python3.6/site-packages/nose/failure.py", line 39, in runTest
raise self.exc_val.with_traceback(self.tb)
File "/.tox/py36/lib/python3.6/site-packages/nose/loader.py", line 418, in loadTestsFromName
addr.filename, addr.module)
File "/.tox/py36/lib/python3.6/site-packages/nose/importer.py", line 47, in importFromPath
return self.importFromDir(dir_path, fqname)
File "/.tox/py36/lib/python3.6/site-packages/nose/importer.py", line 79, in importFromDir
fh, filename, desc = find_module(part, path)
File "/usr/lib/python3.6/imp.py", line 297, in find_module
raise ImportError(_ERR_MSG.format(name), name=name) ImportError: No module named 'my_project'

Answer 1

I see three possible offenders.
(1) python3 setup.py build should not exist in the commands section.
# the build command is redundant, there is a special option for this.
commands = python3 setup.py build
nosetests
# The install command with it's default
install_command=python -m pip install {opts} {packages}(ARGV)
deps = -r{toxinidir}/test-requirements.txt
(2) And with Pycharm you might have added your project as a sources root (right click folder > mark directory as > sources root). Or configured it otherwise (PATH variable perhaps?) that makes my_project available in context to running it in Pycharm? This should not happen inside tox though, unless you have whitelist externals or sitepackages turned to True..
So when installed on a container this link does not exist.
(3) I can't help but notice the abscence of a setup.py or pyproject.toml. Files used to install my_project. E.g. run this command locally and debug your installation if it doesn't work:
pip install .