Customize the error message body

[jesseko]

+1
Very opaque error message and difficult to address

Longer discussion here:

Error while saving single type: Invalid input data. Please verify unique constraints

i had the same error. i had previously created a singe type data with 2 text fields and then i added 2 more text fields to the same single type data, when i tried to fill the newly added text fields it showed me the error, so i tried deleting the whole entry and started filling all the text fields once again, all at once, again and it worked. a solution you might try