`csslint` offers some diagnostics related to all the document without any relevant line number (tested against csslint v0.10.0, the version offered by `npm install -g csslint`).
For example, report could include `<issue severity="warning" reason="You have 2 h4s defined in this stylesheet." evidence=""/>`
In such case, `arc lint` fails and the exception `Parameter passed to "setLine()" must be an integer.` is thrown.
**Sample CSS code to repro**
```
h4 {
font-family: 'Open Sans', Helvetica, Arial, sans-serif;
}
.footer h4 {
color: white;
}
```
**Stacktrace**
```
>>> [8] <exec> $ 'csslint' '--format=lint-xml' '/tmp/ArcanistCSSLintLinter-issue/multi-headings.css'
<<< [6] <lint> 23,149 us
>>> [9] <lint> CSSLint <paths = 1>
<<< [8] <exec> 460,894 us
<<< [9] <lint> 458,375 us
[2015-11-17 04:16:53] EXCEPTION: (PhutilAggregateException) Some linters failed:
- Exception: Parameter passed to "setLine()" must be an integer. at [<arcanist>/src/lint/engine/ArcanistLintEngine.php:274]
arcanist(head=production, ref.master=66ab1c955d27, ref.production=6573dedafdbd), phutil(head=master, ref.master=e9ed72483a14)
#0 <#2> ArcanistLintMessage::validateInteger(string, string) called at [<arcanist>/src/lint/ArcanistLintMessage.php:75]
#1 <#2> ArcanistLintMessage::setLine(string) called at [<arcanist>/src/lint/linter/ArcanistCSSLintLinter.php:72]
#2 <#2> ArcanistCSSLintLinter::parseLinterOutput(string, integer, string, string) called at [<arcanist>/src/lint/linter/ArcanistExternalLinter.php:437]
#3 <#2> ArcanistExternalLinter::resolveFuture(string, ExecFuture) called at [<arcanist>/src/lint/linter/ArcanistFutureLinter.php:34]
#4 <#2> ArcanistFutureLinter::didLintPaths(array) called at [<arcanist>/src/lint/engine/ArcanistLintEngine.php:594]
#5 <#2> ArcanistLintEngine::executeDidLintOnPaths(ArcanistCSSLintLinter, array) called at [<arcanist>/src/lint/engine/ArcanistLintEngine.php:545]
#6 <#2> ArcanistLintEngine::executeLintersOnChunk(array, array) called at [<arcanist>/src/lint/engine/ArcanistLintEngine.php:473]
#7 <#2> ArcanistLintEngine::executeLinters(array) called at [<arcanist>/src/lint/engine/ArcanistLintEngine.php:216]
#8 ArcanistLintEngine::run() called at [<arcanist>/src/workflow/ArcanistLintWorkflow.php:334]
#9 ArcanistLintWorkflow::run() called at [<arcanist>/scripts/arcanist.php:382]
```