Workaround for funky python install on github.

Author: kpeeters

.github/workflows/ccpp.yml

@@ -6,11 +6,16 @@ jobs:
   build:
 
     runs-on: ubuntu-latest
+    python-version: 3.6
 
     steps:
     - uses: actions/checkout@v1
+    - name: setup python
+      uses: actions/setup-python@v2
+      with:
+          python-version: 3.6
     - name: get dependencies
-      run:  sudo apt-get install git cmake python3-dev g++ libpcre3 libpcre3-dev libgmp3-dev libgtkmm-3.0-dev libboost-all-dev libgmp-dev libsqlite3-dev uuid-dev texlive-base python3-mpmath python3-sympy python3-gmpy2 && python3 -c "import sympy; print(sympy.__version__)" 
+      run:  sudo apt-get install git cmake python3-dev g++ libpcre3 libpcre3-dev libgmp3-dev libgtkmm-3.0-dev libboost-all-dev libgmp-dev libsqlite3-dev uuid-dev texlive-base python3-mpmath && python -m pip install sympy
     - name: configure
       run:  mkdir build && cd build && cmake -DENABLE_MATHEMATICA=OFF ..
     - name: make