ResourceWarning while running tests

```shell
$> python -m pytest -s -v -k test_upload dandi
================================================= test session starts ==================================================
platform linux -- Python 3.8.5, pytest-4.6.9, py-1.8.1, pluggy-0.13.0 -- /home/yoh/proj/dandi/dandi-cli/venvs/dev3/bin/python
cachedir: .pytest_cache
hypothesis profile 'default' -> database=DirectoryBasedExampleDatabase('/home/yoh/proj/dandi/dandi-cli/.hypothesis/examples')
rootdir: /home/yoh/proj/dandi/dandi-cli, inifile: tox.ini
plugins: mock-3.2.0, cov-2.10.0, xdist-1.32.0, timeout-1.3.3, forked-1.1.3, hypothesis-4.36.2
collecting ... Exception ignored in:
Traceback (most recent call last):
File "", line 582, in _compile_bytecode
ResourceWarning: unclosed
Exception ignored in:
Traceback (most recent call last):
File "/home/yoh/proj/dandi/dandi-cli/venvs/dev3/lib/python3.8/site-packages/pkg_resources/_vendor/pyparsing.py", line 3320, in streamline
super(ParseExpression,self).streamline()
ResourceWarning: unclosed
Exception ignored in:
Traceback (most recent call last):
File "/home/yoh/proj/dandi/dandi-cli/venvs/dev3/lib/python3.8/site-packages/pkg_resources/_vendor/pyparsing.py", line 3320, in streamline
super(ParseExpression,self).streamline()
ResourceWarning: unclosed
Exception ignored in:
Traceback (most recent call last):
File "/home/yoh/proj/dandi/dandi-cli/venvs/dev3/lib/python3.8/site-packages/pkg_resources/_vendor/pyparsing.py", line 3320, in streamline
super(ParseExpression,self).streamline()
ResourceWarning: unclosed
collected 73 items / 69 deselected / 4 selected
```

@jwodder - any ideas? do you see those?