test_rules.bzl: Make Skylark rule forward compatible
This fixes "type 'depset' is not iterable. Use the `to_list()` method
to get a list." warning.
@@ -206,7 +206,7 @@ def _rule_test_impl(ctx):
# the same file.
generates = sorted(ctx.attr.generates)
generated = sorted([strip_prefix(prefix, f.short_path)
- for f in rule_.files])
+ for f in rule_.files.to_list()])
if generates != generated:
fail("rule %s generates %s not %s"
% (rule_name, repr(generated), repr(generates)))
