downgrade pip for the moment to deal with psf/black#1847

.github/workflows/build_linux.yml

@@ -29,6 +29,9 @@ jobs:
       - name: Install OS dependencies
         run: sudo apt-get install -y libsnappy-dev && pip install python-snappy
       - uses: actions/checkout@v2
+      - name: Downgrade pip
+        # https://github.com/psf/black/issues/1847
+        run: pip install "pip<20.3"
       - name: Install Testing Dependencies
         run: pip install -r developer_requirements.txt
       - name: Run Tests

.github/workflows/build_mac.yml

@@ -43,6 +43,9 @@ jobs:
         run: |
           brew install openblas
           OPENBLAS="$(brew --prefix openblas)" pip install numpy
+      - name: Downgrade pip
+        # https://github.com/psf/black/issues/1847
+        run: pip install "pip<20.3"
       - name: Install Testing Dependencies
         run: pip install -r developer_requirements.txt
       - name: Run Tests

.github/workflows/build_windows.yml

@@ -27,6 +27,9 @@ jobs:
         with:
           python-version: ${{ matrix.py }}
       - uses: actions/checkout@v2
+      - name: Downgrade pip
+        # https://github.com/psf/black/issues/1847
+        run: python -m pip install "pip<20.3"
       - name: Install Testing Dependencies
         run: pip install -r developer_requirements.txt
       - name: Run Tests

.github/workflows/check_formatting.yml

@@ -23,6 +23,9 @@ jobs:
         with:
           python-version: ${{ matrix.py }}
       - uses: actions/checkout@v2
+      - name: Downgrade pip
+        # https://github.com/psf/black/issues/1847
+        run: pip install "pip<20.3"
       - name: Install Testing Dependencies
         run: pip install -r developer_requirements.txt
       - name: Run Black