Simplify and fix pex filenaming.

Makefile

@@ -200,11 +200,8 @@ dist: setrequirements writeversion staticdeps staticdeps-cext strip-staticdeps b
 	python setup.py bdist_wheel
 	ls -l dist
 
-read-whl-file-version:
-	python ./build_tools/read_whl_version.py ${whlfile} > kolibri/VERSION
-
 pex:
-	ls dist/*.whl | while read whlfile; do $(MAKE) read-whl-file-version whlfile=$$whlfile; pex $$whlfile --disable-cache -o dist/kolibri-`cat kolibri/VERSION | sed 's/+/_/g'`.pex -m kolibri --python-shebang=/usr/bin/python3; done
+	ls dist/*.whl | while read whlfile; do version=$$(python ./build_tools/read_whl_version.py $$whlfile); pex $$whlfile --disable-cache -o dist/kolibri-`echo $$version | sed 's/+/_/g'`.pex -m kolibri --python-shebang=/usr/bin/python3; done
 
 i18n-extract-backend:
 	cd kolibri && python -m kolibri manage makemessages -- -l en --ignore 'node_modules/*' --ignore 'kolibri/dist/*' --all

build_tools/read_whl_version.py

@@ -1,16 +1,13 @@
-import logging
 import sys
 
 from pkginfo import Wheel
 
-logger = logging.getLogger(__name__)
-
 if __name__ == "__main__":
     if len(sys.argv) != 2:
-        logger.error("Usage: read_whl_version.py <whl_file>")
+        print("Usage: read_whl_version.py <whl_file>")  # noqa: T201
         sys.exit(1)
 
     whl_file = sys.argv[1]
     whl = Wheel(whl_file)
-    logger.info(whl.version)
+    print(whl.version)  # noqa: T201
     sys.exit(0)