Reference to this forum thread:
user Uwe_Ganswig (German locale) reported Rockstor failing over update process
rpm_build_info fails here expecting a US/UK abbreviated weekday.
Heh, opened an issue for this just seconds after you did. There is also a number format issue (comma as decimal separator) at this place.
Update: check latest messages on Rockstor forum thread
Fixes #1479 by forcing always run_command to be on en_US locale