pre-compile is failing for binary targets if there is no main specified #2881
Description
With #2768 optional, it is possible to have zero .py files or the main is not used or specify main_module.
Then I get errors:
providers = py_executable_impl(
File "/home/ignas-anikevicius/.cache/bazel/_bazel_ignas-anikevicius/e1764a0ec8835154284d951e9bb11b85/external/rules_python+/python/private/py_executable.bzl", line 256, column 35, in py_executable_impl
return py_executable_base_impl(
File "/home/ignas-anikevicius/.cache/bazel/_bazel_ignas-anikevicius/e1764a0ec8835154284d951e9bb11b85/external/rules_python+/python/private/py_executable.bzl", line 1049, column 50, in py_executable_base_impl
main_py = precompile_result.py_to_pyc_map[main_py]
Error: key None not found in dictionary
It seems that we may have forgotten to handle the main_module in precompilation.