I've been playing with remediation code, and I've seen that remediation code for many checks fails due to undefined functions as "populate" (to populate defined variables) and "fix_audit_syscall_rule" (for audit checks)
I've seen that both functions (and many more) are defined inside the datasource, in group xccdf_org.ssgproject.content_group_remediation_functions
Since I'm a complete newbie in openSCAP, I'm not sure how it should work: