Some operations may not run during installation (pre-op mode) since the configuration is not complete yet, and so they may generate exceptions. Currently the CMS.isPreOpMode() is used to conditionally ignore those exceptions if they happen in the pre-op mode, for example:

try {
    ... operation ...
} catch (EBaseException e) {
    if (CMS.isPreOpMode())
        return;
}

However, such code may inadvertently hide actual installation errors that should have been reported to the user. So, rather than ignoring the errors, the code should have avoided executing operations that cannot run in the pre-op mode in the first place, for example:

if (!CMS.isPreOpMode()) {
    ... operation ...
}

Proposed milestone: 10.3.x