Pin version for Python 3.6 support

Poetry 1.2.x drops support for Python 3.7

Author: PeterJCLaw

.circleci/config.yml

@@ -5,7 +5,8 @@ references:
     run:
       name: Install Poetry
       command: |
-        curl -sSL https://install.python-poetry.org | python3 -
+        # Need to use version < 1.2.0 in order to support Python 3.6
+        curl -sSL https://install.python-poetry.org | python3 - --version 1.1.15
   restore-dependencies-cache: &restore-dependencies-cache
     restore_cache:
       keys: