use 'python -mpip' to work around macOS problems

common_utils.sh

@@ -333,18 +333,13 @@ function install_wheel {
     #     WHEEL_SDIR  (optional, default "wheelhouse")
     #     TEST_DEPENDS  (optional, default "")
     #     MANYLINUX_URL (optional, default "") (via pip_opts function)
-    set -x
     local wheelhouse=$(abspath ${WHEEL_SDIR:-wheelhouse})
     if [ -n "$TEST_DEPENDS" ]; then
         while read TEST_DEPENDENCY; do
-            pip install $(pip_opts) $@ $TEST_DEPENDENCY
+            python -mpip install $(pip_opts) $@ $TEST_DEPENDENCY
         done <<< "$TEST_DEPENDS"
     fi
-    ls .
-    which pip
-    which python
-    pip install packaging
-    get_platform
+    python -mpip install packaging
     local supported_wheels=$(python $MULTIBUILD_DIR/supported_wheels.py $wheelhouse/*.whl)
     if [ -z "$supported_wheels" ]; then
         echo "ERROR: no supported wheels found"
@@ -352,7 +347,7 @@ function install_wheel {
         exit 1
     fi
     # Install compatible wheel
-    pip install $(pip_opts) $@ $supported_wheels
+    python -mpip install $(pip_opts) $@ $supported_wheels
 }
 
 function install_run {