Install missing Python package

Author: Flamefire

.github/workflows/synchronize-launchpad.yml

@@ -23,6 +23,8 @@ jobs:
           . $venv_dir/bin/activate
           echo "VIRTUAL_ENV=$VIRTUAL_ENV" >> "$GITHUB_ENV"
           echo "$venv_dir/bin" >> "$GITHUB_PATH"
+          pip install --upgrade pip
+          pip install Cython
           pip install 'breezy[fastimport,git,launchpad]<3.3'  # 3.3+ requires interactive login
           fastimport_dir=$venv_dir/lib/python*/site-packages/breezy/plugins/fastimport
           # Add missing import and use binary buffer of stdin for Python3 compat