Print line number next to problem in check-names

Signed-off-by: Yuto Takano <yuto.takano@arm.com>
diff --git a/tests/scripts/check-names.py b/tests/scripts/check-names.py
index b1835c6..5878bfa 100755
--- a/tests/scripts/check-names.py
+++ b/tests/scripts/check-names.py
@@ -63,10 +63,15 @@
         self.name = name
 
     def __str__(self):
+        ln_str = str(self.pos[0])
+        gutter_len = max(4, len(ln_str))
+        gutter = (gutter_len - len(ln_str)) * " " + ln_str
+        underline = self.pos[1] * " " + (self.pos[2] - self.pos[1]) * "^"
+
         return (
-            "       |\n" +
-            "       | {}".format(self.line) +
-            "       | " + self.pos[1] * " " + (self.pos[2] - self.pos[1]) * "^"
+            " {0} |\n".format(gutter_len * " ") +
+            " {0} | {1}".format(gutter, self.line) +
+            " {0} | {1}".format(gutter_len * " ", underline)
         )
 
 class Problem(): # pylint: disable=too-few-public-methods