test_subprocess: use surrogateescape error handler to write shell scripts
test_subprocess: use surrogateescape error handler to write shell scripts

test_args_string() and test_call_string() create shell scripts including the
path to the Python executable: use surrogateescape to encode paths including
surrogate characters.

sk-/python2.7-type-annotator,sk-/python2.7-type-annotator,sk-/python2.7-type-annotator