[Originally from bubblewrap commits c5c999a7 "tests: test --userns" and 3e5fe1bf "tests: Better error message if assert_files_equal fails"; separated into this commit by Simon McVittie.]
[Originally from bubblewrap commits c5c999a7 "tests: test --userns" and 3e5fe1bf "tests: Better error message if assert_files_equal fails"; separated into this commit by Simon McVittie.]