Build python package in virtualenv (#3529)

Author: Code0x58

scripts/packages/BUILD

@@ -605,6 +605,8 @@ genrule(
         "export RELEASE_FILE_DIR=$$(pwd)",
         "export TMP_DIR=$$(mktemp -d -t heronpy.XXXXX)",
         "echo $$TMP_DIR",
+        "$(location @virtualenv//:virtualenv) --no-download --quiet --clear $$TMP_DIR/venv",
+        "PS1= source $$TMP_DIR/venv/bin/activate",
         "export HERONPY_DIR=$$TMP_DIR/heronpy",
         "export HERONPYAPI_UNZIP=$$TMP_DIR/heronapiunzip",
         "export HERONPYSTREAMLET_UNZIP=$$TMP_DIR/heronstreamletunzip",
@@ -660,6 +662,7 @@ genrule(
         "//heronpy/connectors:heron-pythonconnectors-package",
         "//heronpy/proto:proto-py-package",
         "//heronpy/streamlet:heron-python-streamlet-api-package",
+        "@virtualenv",
     ],
 )