Don't hide error messages with invalid UTF-8 chars
Occasionally transfers fails with not so clear error message that looks like
TRANSFER [13] TRANSFER ERROR: Copy failed with mode 3rd pull, with error: Error string contains not valid UTF-8 chars
because davix2gliberr
replace all errors with wrong UTF-8 encoding to the same message Error string contains not valid UTF-8 chars
. Removing completely text of error message doesn't help to diagnose transfer failures so this update just normalize whole error message that comes from davix to the valid UTF-8 string that is set as gfal2_set_error
.