.github/workflows/master.yml: don't run with 3.6.7

Author: zachetienne

.github/workflows/master.yml

@@ -16,10 +16,7 @@ jobs:
     strategy:
       matrix:
        os: ['ubuntu-20.04', 'ubuntu-22.04']
-       python-version: ['3.6.7', '3.7.13', '3.8.18', '3.9.19', '3.x']
-       exclude:
-         - os: 'ubuntu-22.04'
-           python-version: '3.6.7'
+       python-version: ['3.7.13', '3.8.18', '3.9.19', '3.x']
 
     steps:
     - uses: actions/checkout@v4
@@ -36,7 +33,7 @@ jobs:
       run: |
         python -m pip install --upgrade pip
         pip install -U -r requirements.txt
-        if [[ "${{ matrix.python-version }}" != "3.6.7" && "${{ matrix.python-version }}" != "3.7.13" ]]; then
+        if [[ "${{ matrix.python-version }}" != "3.7.13" ]]; then
           pip install -U -r requirements-dev.txt
         else
           # Install packages from requirements-dev.txt except those with a fixed version.
@@ -47,7 +44,7 @@ jobs:
 
     - name: Install sympy or DEVELOPMENT sympy based on Python version
       run: |
-        if [[ "${{ matrix.python-version }}" != "3.6.7" && "${{ matrix.python-version }}" != "3.7.13" ]]; then
+        if [[ "${{ matrix.python-version }}" != "3.7.13" ]]; then
           pip install git+https://github.com/sympy/sympy.git
         else
           pip install sympy
@@ -58,8 +55,8 @@ jobs:
         echo "Running CI tests with SymPy version = $(isympy --version)"
         echo "Running CI tests with clang-format version = $(clang-format --version)"
 
-    - name: Check mypy and black versions when Python != 3.6.7 and != 3.7.13 chosen (they are too broken in those Python versions).
-      if: matrix.python-version != '3.6.7' && matrix.python-version != '3.7.13'
+    - name: Check mypy and black versions when != 3.7.13 chosen (they are too broken in those Python versions).
+      if: matrix.python-version != '3.7.13'
       run: |
         mypy --version
         black --version
@@ -76,17 +73,17 @@ jobs:
           echo "-={ $python_file }=-"
           echo "-={ Step 1: Doctests/run Python module }=-"
           DOCTEST_MODE=1 PYTHONPATH=.:$PYTHONPATH python $python_file || { failed_tests+=("doctest in $python_file"); break; }
-          # Turns out that black in Python 3.6 & 3.7 has a heart attack when parsing equations/general_relativity/BSSN_quantities.py:
+          # Turns out that black in Python 3.7 has a heart attack when parsing equations/general_relativity/BSSN_quantities.py:
           # INTERNAL ERROR: Black produced code that is not equivalent to the source. Please report a bug on ....
-          if [[ "${{ matrix.python-version }}" != "3.6.7" && "${{ matrix.python-version }}" != "3.7.13" && "${{ matrix.python-version }}" != "3.8.18" ]]; then
+          if [[ "${{ matrix.python-version }}" != "3.7.13" && "${{ matrix.python-version }}" != "3.8.18" ]]; then
             echo "-={ Step 2: black $python_file }=-"
             black --check $python_file || { failed_tests+=("black in $python_file"); break; }
             echo "-={ Step 3: mypy }=-"
             PYTHONPATH=.:$PYTHONPATH mypy --strict --pretty --allow-untyped-calls $python_file || { failed_tests+=("mypy in $python_file"); break; }
           fi
           echo "-={ Step 4: pylint }=-"
           pylint_score="0"
-          if [[ "${{ matrix.python-version }}" == "3.6.7" || "${{ matrix.python-version }}" == "3.7.13" ]]; then
+          if [[ "${{ matrix.python-version }}" == "3.7.13" ]]; then
             pylint_score=$(PYTHONPATH=.:$PYTHONPATH pylint --rcfile=.pylintrc_python36 $python_file | tail -2 | grep -Eo '[0-9\.]+' | head -1 || echo "0")
           else
             pylint_score=$(PYTHONPATH=.:$PYTHONPATH pylint --rcfile=.pylintrc $python_file | tail -2 | grep -Eo '[0-9\.]+' | head -1 || echo "0")