gRPC packages: declared proto package, directory structure

[geigerj]

cc: @bjwatson @tbetbetbe

If you attempt to build a Python gRPC package for foo/bar/service.proto, it generates the Python package foo.bar.service, even if service.proto declares a different package like

// service.proto
syntax = proto3;

package foo.baz

In this case, GAPIC will attempt to generate an import of service as the Python module foo.baz.service rather than foo.bar.service.

It might be nice if packman could detect this discrepancy and either

• Issue a warning to the console, or
• Fix the protoc output so that it uses the declared package foo.baz