build/pkgs/sagelib/spkg-install: Remove installed sage/__init__.py

build/pkgs/sagelib/spkg-install

@@ -38,6 +38,7 @@ export SAGE_SHARE=/doesnotexist
 # export SAGE_DOC=/doesnotexist
 
 SITEPACKAGESDIR=$(python3 -c 'import sysconfig; print(sysconfig.get_paths()["purelib"])')
+
 if [ "$SAGE_EDITABLE" = yes ]; then
     # In an incremental build, we may need to uninstall old versions installed by distutils
     # under the old distribution name "sage" (before #30912, which switched to setuptools
@@ -46,6 +47,9 @@ if [ "$SAGE_EDITABLE" = yes ]; then
     (cd "$SITEPACKAGESDIR" && rm -rf sage sage_setup sage-[1-9]*.egg-info sage-[1-9]*.dist-info)
     time python3 -m pip install --verbose --no-deps --no-index --no-build-isolation --isolated --editable . || exit 1
 else
+    # Make sure that an installed old version of sagelib in which sage is an ordinary package
+    # does not shadow the namespace package sage during the build.
+    (cd "$SITEPACKAGESDIR" && rm -f sage/__init__.py)
     # Likewise, we should remove the egg-link that may have been installed previously.
     (cd "$SITEPACKAGESDIR" && rm -f sagemath-standard.egg-link)
     time python3 -u setup.py --no-user-cfg build install || exit 1