Set default PY in cargo wrapper (#7195)
Set default PY in cargo wrapper (#7195)

It calls virtualenv so needs one set. Some scripts call it bare.
pantsbuild/pants,tdyas/pants,tdyas/pants,benjyw/pants,twitter/pants,benjyw/pants,twitter/pants,pantsbuild/pants,wisechengyi/pants,benjyw/pants,pantsbuild/pants,tdyas/pants,tdyas/pants,benjyw/pants,wisechengyi/pants,tdyas/pants,benjyw/pants,twitter/pants,pantsbuild/pants,jsirois/pants,pantsbuild/pants,benjyw/pants,benjyw/pants,wisechengyi/pants,tdyas/pants,twitter/pants,wisechengyi/pants,twitter/pants,wisechengyi/pants,twitter/pants,jsirois/pants,wisechengyi/pants,wisechengyi/pants,twitter/pants,tdyas/pants,wisechengyi/pants,wisechengyi/pants,tdyas/pants,pantsbuild/pants,twitter/pants,twitter/pants,tdyas/pants,jsirois/pants,pantsbuild/pants