On `/diffusion/edit/1/page/encoding/`,
* enter a valid encoding, such as "7bit", get success message
* enter a valid encoding with random capitalization, such as "7biT", get success message
* enter a valid alias encoding, such as "ISO-10646-UCS-2", get success message
* enter a valid alias encoding with random capitalization, such as "isO-10646-uCS-2", get success message
* enter an invalid encoding, such as "whatever", get error message "Repository encoding "whatever" is not valid: String conversion from encoding 'UTF-8' to encoding 'whatever' failed:"
In any case, no exception is shown anymore.