Fix errors with incompatible_disallow_empty_glob (#315)
Fix errors with incompatible_disallow_empty_glob (#315)

Allow py_library sources to be empty.
If --incompatible_disallow_empty_glob is set then generated py_library
targets will fail if there are no .py files.

Examples are pymssql==2.1.4 and cx-Oracle==7.2.3.

Set `allow_empty = True` for glob().

Bazel issue for incompatible_disallow_empty_glob:
https://github.com/bazelbuild/bazel/issues/8195

Co-authored-by: Andy Scott <b5f96d75726e2bad48980205c34a1ab7a34879bb@users.noreply.github.com>
bazelbuild/rules_python,bazelbuild/rules_python,bazelbuild/rules_python