Rudder

If we create a technique, with a parameter finishing with \ , we get an error message at save
But the file is still saved, and when we go back to tehcnique editor we have again a message

An Error occured! Could not parse Technique 'invalid_technique'
Details:

 caused by : Error while running post-hook command cf-promises -pjson -f /var/rudder/configuration-repository/ncf/50_techniques/invalid_technique/invalid_technique.cf
/var/rudder/configuration-repository/ncf/50_techniques/invalid_technique/invalid_technique.cf:9:126: error: syntax error
    "method_call_context_0" usebundle => _method_reporting_context("File absent", "/tmp/some_broken_file\");
                                                                                                                             ^
/var/rudder/configuration-repository/ncf/50_techniques/invalid_technique/invalid_technique.cf:9:126: error: Invalid function argument, wrong input 'method_call'
    "method_call_context_0" usebundle => _method_reporting_context("File absent", "/tmp/some_broken_file\");
                                                                                                                             ^
/var/rudder/configuration-repository/ncf/50_techniques/invalid_technique/invalid_technique.cf:9:154: error: Expected ',', wrong input '" usebundle => file_absent("'
    "method_call_context_0" usebundle => _method_reporting_context("File absent", "/tmp/some_broken_file\");
                                                                                                                                                         ^
/var/rudder/configuration-repository/ncf/50_techniques/invalid_technique/invalid_technique.cf:9:155: error: Invalid function argument, wrong input '/'
    "method_call_context_0" usebundle => _method_reporting_context("File absent", "/tmp/some_broken_file\");
                                                                                                                                                          ^
/var/rudder/configuration-repository/ncf/50_techniques/invalid_technique/invalid_technique.cf:9:158: error: Expected ',', wrong input 'tmp'
    "method_call_context_0" usebundle => _method_reporting_context("File absent", "/tmp/some_broken_file\");

The only way to get out of that is to modify the .cf file

We should be able to check the file before saving, or if it's not possible, save it somewhere safe first, validate, and move it to final position

Targeting to 4.3, but the full lfix may be too hard to get there