Flag --incompatible_no_implicit_file_export will break rules_appengine in a future Bazel release

[bazel-flag-bot]

Incompatible flag --incompatible_no_implicit_file_export will be enabled by default in a future Bazel release [1], thus breaking rules_appengine.

The flag is documented here: bazelbuild/bazel#10225

Please check the following CI builds for build and test results:

• Ubuntu 18.04, OpenJDK 11
• Ubuntu 16.04, OpenJDK 8
• macOS, OpenJDK 8

Never heard of incompatible flags before? We have documentation that explains everything.

If you don't want to receive any future issues for rules_appengine or if you have any questions,
please file an issue in https://github.com/bazelbuild/continuous-integration

Important: Please do NOT modify the issue title since that might break our tools.

[1] The target release hasn't been determined yet. Our tool will update the issue title once the flag flip has been scheduled.

[pmbethe09]

@vladmos do you know how to fix this?

[fweikert]

Someone in the Bazel team should fix @remote_coverage_tools