Merge pull request #16663 from mppf/fix-venv

Replace symbolic link python3 in venv with wrapper

Follow-up to PRs #16644 and #16560.

This PR is intended to solve problems where this warning is reported in some nightly testing configurations:
```
[Warning: could not import filelock]
```

The venv normally includes in some-venv/bin/python3 a symbolic link to
the real python3 interpreter used.

This has the drawback that when distributing the venv, the relevant
python executable might be in a different place.

So, this commit adds a bash script that runs python while telling it to
think it is being launched from that location (that is what the exec -a
here does). The wrapper uses whichever python3 is available in the
system. This allows the python3 being run to change (e.g. if the venv is
used on a system with a different path to the python3).

This approach replaces the approach from PR #3571.

Reviewed by @ronawho - thanks!

- [x] checked basic module build on an XC
- [x] full local testing

Makefile.devel

@@ -18,8 +18,6 @@
 
 export CHPL_MAKE_PYTHON := $(shell $(CHPL_MAKE_HOME)/util/config/find-python.sh)
 
-PYTHON_VERSION_DIR = py$(shell $(CHPL_MAKE_PYTHON) $(CHPL_MAKE_HOME)/util/chplenv/chpl_python_version.py)
-
 develall:
 	@$(MAKE) always-build-man
 	@$(MAKE) always-build-chplspell-venv

third-party/chpl-venv/Makefile

@@ -77,6 +77,8 @@ $(CHPL_VENV_VIRTUALENV_DIR):
 	export VIRTUAL_ENV=$(CHPL_VENV_VIRTUALENV_DIR) && \
 	$(PIP) install \
 	--upgrade $(CHPL_PIP_INSTALL_PARAMS) $(LOCAL_PIP_FLAGS) wheel && \
+	rm  $(CHPL_VENV_VIRTUALENV_BIN)/python3
+	cp python3-wrapper $(CHPL_VENV_VIRTUALENV_BIN)/python3
 	touch $(CHPL_VENV_VIRTUALENV_DIR)
 
 # Phony convenience target for creating virtualenv.
@@ -153,7 +155,7 @@ rm-chplspell-reqs: FORCE
 # Python installation (ie, the Python used was not installed under "/usr/...").
 # Only applicable when building a Cray Chapel module under certain conditions.
 use-system-python: FORCE
-	@$(PYTHON) ./venv-use-sys-python.py $(CHPL_VENV_INSTALL_DIR)
+	@echo ignoring use-system-python
 
 FORCE:
 

third-party/chpl-venv/python3-wrapper

@@ -0,0 +1,13 @@
+#!/usr/bin/env bash
+
+# Remove the directory containing this script from the path
+# (here we just replace chpl-venv with missing since we know
+#  chpl-venv is always part of the PATH component to this script)
+
+# This is to avoid an infinite loop running this script over and over.
+export PATH=${PATH//chpl-venv/missing}
+
+# Now run the real python3 interpreter but tell it that it
+# is being launched at the current path, so it can
+# correctly find dependencies in the venv
+exec -a "$0" python3 "$@"