it did not work for hex encoded obj_id.
Also:
- tests/pathslicing: improve tests for the check() method validate we do have the expected error, namely 'not a gzip' and 'wrong hash id'.
- pathslicing: fix the 'not a gzip' error message in check() write the hex obj id in the error message instead of the repr of the bytes.
- tests/pathslicing: add a test for check() that ensure it does work we only had tests for non-valid checks.
- Fixes test_objstorage_pathslicing.py's test_check_not_gzip.
- Fixes test_objstorage_pathslicing.py's test_check_ok.