Cleanup the python/pep257 checker.

syntax_checkers/python/pep257.vim

@@ -14,21 +14,32 @@ function! SyntaxCheckers_python_pep257_IsAvailable()
     return executable('pep257')
 endfunction
 
+" sanity: kill empty lines here rather than munging errorformat
+function! SyntaxCheckers_python_pep257_Preprocess(errors)
+    return filter(copy(a:errors), 'v:val != ""')
+endfunction
+
 function! SyntaxCheckers_python_pep257_GetLocList()
     let makeprg = syntastic#makeprg#build({
         \ 'exe': 'pep257',
         \ 'filetype': 'python',
         \ 'subchecker': 'pep257' })
 
-    let errorformat = '%f:%l:%c: %m'
+    let errorformat =
+        \ '%E%f:%l:%c%\%.%\%.%\d%\+:%\d%\+: %m,' .
+        \ '%E%f:%l:%c: %m,' .
+        \ '%+C    %m'
 
     let loclist = SyntasticMake({
         \ 'makeprg': makeprg,
         \ 'errorformat': errorformat,
-        \ 'subtype': 'Style' })
+        \ 'subtype': 'Style',
+        \ 'preprocess': 'SyntaxCheckers_python_pep257_Preprocess',
+        \ 'postprocess': ['compressWhitespace'] })
 
+    " pep257 outputs byte offsets rather than column numbers
     for n in range(len(loclist))
-        let loclist[n]['type'] = loclist[n]['text'] =~? '^W' ? 'W' : 'E'
+        let loclist[n]['col'] = get(loclist[n], 'col', 0) + 1
     endfor
 
     return loclist