Looks like the pip_generate executable (osx) has a hardcoded path from a user home directory:
/bazel-bin/external/com_bluecore_rules_pyz/pypi/pip_generate_wrapper -requirements requirements.txt -outputDir third_party/pypi -wheelURLPrefix http://example.com/ -wheelDir wheels
panic: open third_party/pypi/pypi_rules.bzl: no such file or directory
goroutine 1 [running]:
main.main()
/Users/evanjones/t/rules_pyz/pypi/pip_generate.go:340 +0x4546
Why not use rules_go to build this directly?