Warning clutters output of cjdk exec (macOS)

[marktsuchida]

The CLI exec command on macOS (arm64) often produces a warning like this:

$ cjdk -j temurin-jre:17 --index-ttl=0 exec java -version
/opt/homebrew/Cellar/[email protected]/3.9.13_1/Frameworks/Python.framework/Versions/3.9/lib/python3.9/multiprocessing/resource_tracker.py:216: UserWarning: resource_tracker: There appear to be 1 leaked semaphore objects to clean up at shutdown
  warnings.warn('resource_tracker: There appear to be %d '
openjdk version "17.0.3" 2022-04-19
OpenJDK Runtime Environment Temurin-17.0.3+7 (build 17.0.3+7)
OpenJDK 64-Bit Server VM Temurin-17.0.3+7 (build 17.0.3+7, mixed mode)

It is seen only if a download occurred (including of the index), and only with exec (i.e., not with java-home).

Of our immediate dependencies, only tqdm uses multiprocessing (tqdm is called even when progress bars are hidden, including for index download). Deleting all uses of tqdm does in fact get rid of the warning.

So this looks similar to conda/conda#9589 (whose resolution (or lack thereof) is not immediately clear to me). It may be python/cpython#90549, which is fixed in trunk and backported to the next Python 3.10 release. (Or maybe not; it could be more specific to the use of os.exec*.)