Dart pub now expects that file to be present in a Flutter SDK (see https://dart.googlesource.com/pub/+/dce232ec195df802a730eb3a66163e28d2ec6444)
This directory contains tests for specific flutter commands.
Tests that are self-contained unit tests should go in hermetic/.
Tests that are more end-to-end, e.g. that involve actually running
subprocesses, should go in permeable/.
The ../../tool/coverage_tool.dart script (which is used to collect
coverage for the tool) runs only the tests in the hermetic directory
when collecting coverage.