Cannot iterate over a depset in Bazel 0.27

[apt-itude]

Starting in Bazel 0.27, depsets will no longer be iterable without passing the --incompatible_depset_is_not_iterable=false flag (see bazelbuild/bazel#5816).

This results errors such as the following:

ERROR: /Users/athompson/code/bazel-javascript/examples/react-app-javascript/src/BUILD.bazel:5:1: in js_library rule //src:src:
Traceback (most recent call last):
	File "/Users/athompson/code/bazel-javascript/examples/react-app-javascript/src/BUILD.bazel", line 5
		js_library(name = 'src')
	File "/private/var/tmp/_bazel_athompson/b5cf6c1c8373f2d1d578c3715ed88e15/external/bazel_javascript/internal/js_library/rule.bzl", line 71, in _js_library_impl
		_js_library_create_full_src(ctx, internal_deps, npm_packages)
	File "/private/var/tmp/_bazel_athompson/b5cf6c1c8373f2d1d578c3715ed88e15/external/bazel_javascript/internal/js_library/rule.bzl", line 99, in _js_library_create_full_src
		ctx.actions.run(inputs = (([ctx.attr._internal_p...), <4 more arguments>)
	File "/private/var/tmp/_bazel_athompson/b5cf6c1c8373f2d1d578c3715ed88e15/external/bazel_javascript/internal/js_library/rule.bzl", line 104, in ctx.actions.run
		[d[JsLibraryInfo].compiled_javascript_dir for d in internal_deps]
type 'depset' is not iterable. Use the `to_list()` method to get a list. Use --incompatible_depset_is_not_iterable=false to temporarily disable this check.
ERROR: Analysis of target '//src:src' failed; build aborted: Analysis of target '//src:src' failed; build aborted```