Force Python 3.6.5 for building on macOS

.circleci/config.yml

@@ -21,6 +21,30 @@ jobs:
             sudo systemsetup -settimezone Europe/Warsaw
             echo "Today is $(date +"%Y-%m-%d %T")"
 
+      - run:
+          name: Set ENV variables
+          command: |
+            echo 'export HOMEBREW_NO_AUTO_UPDATE=1' >> ~/.envs
+
+      - run:
+          name: Install Python version 3.6.5 & readline 7.0.5
+          command: |
+            source ~/.envs
+            curl -o /usr/local/Homebrew/Library/Taps/homebrew/homebrew-core/Formula/python.rb https://raw.githubusercontent.com/Homebrew/homebrew-core/f2a764ef944b1080be64bd88dca9a1d80130c558/Formula/python.rb
+            curl -o /usr/local/Homebrew/Library/Taps/homebrew/homebrew-core/Formula/readline.rb https://raw.githubusercontent.com/Homebrew/homebrew-core/b1bd1c4a62e1336422de3614d1fc49ffbce589a8/Formula/readline.rb
+            # remove check for old compilers which creates the error described in https://github.com/sashkab/homebrew-python/issues/36
+            sed -i.bak -e '58,61d' /usr/local/Homebrew/Library/Taps/homebrew/homebrew-core/Formula/python.rb
+            brew unlink python
+            brew uninstall --ignore-dependencies readline
+            brew install readline
+            brew info readline
+            brew pin readline
+            # --ignore-dependencies is used to prevent this issue: https://github.com/tensorflow/tensorflow/issues/25093
+            brew install --ignore-dependencies python
+            brew switch python 3.6.5_1
+            brew info python
+            brew pin python
+
       - run:
           name: Installed python and pip version
           command: |