fix: avoid fake formatter err

[Shane-XB-Qian]

seems it is difficult to know it was really formatter not supported or it was done in place, perhaps just better to leave it (code fs content) as it was if failed, and not giving maybe incorrect err msg.

[mattn]

Which formatter did you use?

[Shane-XB-Qian]

Which formatter did you use?

should be 'protolint' if i recall correctly.

-- shane.xb.qian