Ignore errors not in linted file

linter.py

@@ -20,8 +20,23 @@ class Ruby(RubyLinter):
     syntax = ('ruby', 'ruby on rails', 'rspec')
     cmd = 'ruby -wc'
     regex = (
-        r'^.+?:(?P<line>\d+): (?:(?P<error>.*?error)|(?P<warning>warning))[,:] (?P<message>[^\r\n]+)\r?\n'
+        r'^(?P<file>.+?):(?P<line>\d+): (?:(?P<error>.*?error)|(?P<warning>warning))[,:] (?P<message>[^\r\n]+)\r?\n'
         r'(?:^[^\r\n]+\r?\n^(?P<col>.*?)\^)?'
     )
     multiline = True
     comment_re = r'\s*#'
+
+    def split_match(self, match):
+        """
+        Return the components of the match.
+
+        We override this because unrelated library files can throw errors,
+        and we only want errors from the linted file.
+
+        """
+
+        if match:
+            if match.group('file') != '-':
+                match = None
+
+        return super().split_match(match)