CI: Run flake8 in isolated environment, simplify invocation

Author: effigies

.github/workflows/test.yml

@@ -39,7 +39,7 @@ jobs:
         python -m pip install .
     - name: Lint
       run: |
-        flake8 --ignore N802,N806,W504 --select W503 `find . -name \*.py | grep -v setup.py | grep -v version.py | grep -v __init__.py | grep -v /docs/`
+        pipx run flake8 --ignore N802,N806,W504 --select W503 nitime/ tools/
     - name: Test
       run: |
         cd && mkdir for_test && cd for_test && pytest --pyargs nitime --cov-report term-missing --cov=AFQ

requirements-dev.txt

@@ -3,4 +3,3 @@ pytest
 pytest-cov
 nibabel
 networkx
-flake8