BREAKING: CssSyntaxError in imported file now throws instead of warns

Closes #264

index.js

@@ -210,10 +210,6 @@ function resolveImportId(result, stmt, options, state) {
         return statements ? result.concat(statements) : result
       }, [])
     })
-    .catch(err => {
-      if (err.message.indexOf("Failed to find") !== -1) throw err
-      result.warn(err.message, { node: atRule })
-    })
 }
 
 function loadImportContent(result, stmt, filename, options, state) {

test/fixtures/imports/syntax-error.css

@@ -0,0 +1,7 @@
+body {
+  bar: bar;
+  qux: qux;
+
+a {
+  foo: foo;
+}

test/fixtures/syntax-error.css

@@ -0,0 +1,6 @@
+@import "syntax-error.css";
+
+syntax.error {
+  /* Error isn't here, it's in the imported file */
+  color: green;
+}

test/syntax-error.js

@@ -0,0 +1,16 @@
+// builtin tooling
+import fs from "fs"
+
+// external tooling
+import test from "ava"
+import postcss from "postcss"
+
+// plugin
+import atImport from ".."
+
+test("SyntaxError in imported file throws", t => {
+  return postcss(atImport({ path: "test/fixtures/imports" }))
+    .process(fs.readFileSync("test/fixtures/syntax-error.css", "utf8"))
+    .then(() => t.fail("should error out"))
+    .catch(err => t.truthy(err))
+})