Add flake8 in conda

Author: Vianney Taquet

.github/workflows/test.yml

@@ -39,7 +39,7 @@ jobs:
         python-version: ${{ matrix.python-version }}
         channels: defaults, conda-forge
     - name: Install dependencies
-      run: conda install codecov mypy numpy=${{ matrix.numpy-version }} scikit-learn pandas pytest-cov typed-ast
+      run: conda install codecov flake8 mypy numpy=${{ matrix.numpy-version }} scikit-learn pandas pytest-cov typed-ast
     - name: Check linting
       run: flake8 . --exclude=doc
     - name: Check static typing