Upgrade the Cython version whenever we can

tools/internal_ci/macos/grpc_build_artifacts.sh

@@ -21,11 +21,11 @@ cd $(dirname $0)/../../..
 source tools/internal_ci/helper_scripts/prepare_build_macos_rc
 
 # install cython for all python versions
-python2.7 -m pip install cython setuptools wheel
+python2.7 -m pip install -U cython setuptools wheel
-python3.5 -m pip install cython setuptools wheel
+python3.5 -m pip install -U cython setuptools wheel
-python3.6 -m pip install cython setuptools wheel
+python3.6 -m pip install -U cython setuptools wheel
-python3.7 -m pip install cython setuptools wheel
+python3.7 -m pip install -U cython setuptools wheel
-python3.8 -m pip install cython setuptools wheel
+python3.8 -m pip install -U cython setuptools wheel
 
 # needed to build ruby artifacts
 time bash tools/distrib/build_ruby_environment_macos.sh

tools/run_tests/helper_scripts/build_python.sh

@@ -175,10 +175,10 @@ case "$VENV" in
   ;;
 esac
 
-$VENV_PYTHON -m pip install --upgrade pip==10.0.1
+$VENV_PYTHON -m pip install --upgrade pip
-$VENV_PYTHON -m pip install setuptools
+$VENV_PYTHON -m pip install --upgrade setuptools
-$VENV_PYTHON -m pip install cython
+$VENV_PYTHON -m pip install --upgrade cython
-$VENV_PYTHON -m pip install six enum34 protobuf
+$VENV_PYTHON -m pip install --upgrade six enum34 protobuf
 
 if [ "$("$VENV_PYTHON" -c "import sys; print(sys.version_info[0])")" == "2" ]
 then