Apply a few suggestions from refurb

[DimitriPapadopoulos]

These refurb suggestions appear to improve readability.

The changes seem trivial to me, hence the lack of news fragment.

Thanks for contributing, make sure you address all the checklists (for details on how see development documentation)

• ran the linter to address style issues (tox -e fix)
• wrote descriptive pull request text
• ensured there are test(s) validating the fix
• added news fragment in docs/changelog folder
• updated/extended the documentation

[gaborbernat]

I don't agree with most of these .

[DimitriPapadopoulos]

I don't agree with most of these .

Why?

• The return is missing from the next function. Either add it to write(), or remove it from read():
  

  virtualenv/src/virtualenv/app_data/na.py

  Lines 54 to 60 in 390ed2a

  	def read(self):
  	"""Nothing to read."""
  	return
  	def write(self, content):
  	"""Nothing to write."""

• What's the point of converting a str literal to a str?
  

  virtualenv/tests/conftest.py

  Lines 189 to 190 in 390ed2a

  	COV_ENV_VAR = "COVERAGE_PROCESS_START"
  	COVERAGE_RUN = os.environ.get(str(COV_ENV_VAR))

• The or instead of if ... else is used in tox, so it cannot be that bad. See for example:
  https://github.com/tox-dev/tox/blob/85ce052d60aadb4fce779c404c052074bc530fbc/src/tox/config/loader/api.py#L63