Plan

1. run the UPDATE 52x_Modules` SET AppliedDBRevisions = '' WHERE Name = 'Custom';` to forget last executed deployment scripts
2. change to modules/custom/install/project_upgrades.sql file to look like this:

# r1: Initial Project Task (#TASK_ID)
SELECT FirstName FROM `52x_Users`;
# some comment above error
ERROR1 ERROR2 ERROR3
SELECT LastName FROM `52x_Users`;
# some comment below error

3. login to Admin Console
4. go to Tools → System Tools section
5. use the Deploy button
6. confirm, that:
   • SQLs after ERROR1 ERROR2 ERROR3 line wasn't shown
   • error wasn't logged into Logs & Reports → System Log section
7. get the value of the LogUniqueId field from any record of the 52x_SystemLog database table
8. in the /index.php file add $application->deleteLog(LOG_UNIQUE_ID_HERE) after $application->Init(); line
9. access changed /index.php file from web browser
10. confirm, that log record was deleted