Doesn't handle config misconfiguration

[ErikReider]

Gnomes default config for Vala includes some options that are deprecated and unknown. When only deprecated options exist (no unknown), the formatter includes the uncrustify warning message in the temp file created. When a unknown option is used, the formatter command returns a 1.

vim-uncrustify/plugin/uncrustify.vim

Line 70 in ec68cfe

let result = system(cmd)

When running uncrustify in the terminal, the formatted runs as usual even with the strange options.
The options used are:

deprecated: sp_cpp_lambda_paren = force
deprecated: sp_word_brace = ignore
unknown: align_number_left = false

Everything works as expected when commenting those lines out

[cofyc]

can you help fix this? I don't have time to work on it.