use conda for pyflakes

Author: simonjayhawkins

environment.yml

@@ -21,6 +21,7 @@ dependencies:
   - flake8<3.8.0  # temporary pin, GH#34150
   - flake8-comprehensions>=3.1.0  # used by flake8, linting of unnecessary comprehensions
   - flake8-rst>=0.6.0,<=0.7.0  # linting of code blocks in rst files
+  - pyflakes>=2.2.0  # minimum version to support mypy error codes
   - isort=4.3.21  # check that imports are in the right order
   - mypy=0.730
   - pycodestyle  # used by flake8
@@ -109,4 +110,3 @@ dependencies:
   - pip:
     - git+https://github.com/pandas-dev/pydata-sphinx-theme.git@master
     - git+https://github.com/numpy/numpydoc
-    - pyflakes>=2.2.0

requirements-dev.txt

@@ -11,6 +11,7 @@ cpplint
 flake8<3.8.0
 flake8-comprehensions>=3.1.0
 flake8-rst>=0.6.0,<=0.7.0
+pyflakes>=2.2.0
 isort==4.3.21
 mypy==0.730
 pycodestyle
@@ -73,5 +74,4 @@ cftime
 pyreadstat
 tabulate>=0.8.3
 git+https://github.com/pandas-dev/pydata-sphinx-theme.git@master
-git+https://github.com/numpy/numpydoc
-pyflakes>=2.2.0
+git+https://github.com/numpy/numpydoc