fix(ruby): use stdout stream to raise exceptions from bundler

- relevant error information is in stdout instead of stderr for bundler.

aws_lambda_builders/workflows/ruby_bundler/bundler.py

@@ -48,9 +48,10 @@ def run(self, args, cwd=None):
 
  p = self.osutils.popen(invoke_bundler, stdout=self.osutils.pipe, stderr=self.osutils.pipe, cwd=cwd)
 
- out, err = p.communicate()
+ out, _ = p.communicate()
 
  if p.returncode != 0:
- raise BundlerExecutionError(message=err.decode("utf8").strip())
+ # Bundler has relevant information in stdout, not stderr.
+ raise BundlerExecutionError(message=out.decode("utf8").strip())
 
  return out.decode("utf8").strip()

tests/unit/workflows/ruby_bundler/test_bundler.py

@@ -58,7 +58,7 @@ def test_returns_popen_out_decoded_if_retcode_is_0(self):
 
  def test_raises_BundlerExecutionError_with_err_text_if_retcode_is_not_0(self):
  self.popen.returncode = 1
- self.popen.err = b"some error text\n\n"
+ self.popen.out = b"some error text\n\n"
  with self.assertRaises(BundlerExecutionError) as raised:
  self.under_test.run(["install", "--without", "development", "test"])
  self.assertEqual(raised.exception.args[0], "Bundler Failed: some error text")