utils/check-package: check ignored files exist

When an ignored file is removed (e.g. a package patch is no longer
needed after a version bump), the corresponding entry in the ignore list
is no longer needed.

However, we currently only validate that an ignored *test* still fails,
not that a ignore files is now missing.

Add a new test to check-package that does that check, and add a
test-case for that check.

Signed-off-by: Yann E. MORIN <yann.morin.1998@free.fr>
Cc: Ricardo Martincoski <ricardo.martincoski@gmail.com>

utils/checkpackagelib/lib_ignore.py

@@ -0,0 +1,14 @@
+# See utils/checkpackagelib/readme.txt before editing this file.
+
+import os
+
+from checkpackagelib.base import _CheckFunction
+
+
+class IgnoreMissingFile(_CheckFunction):
+    def check_line(self, lineno, text):
+        fields = text.split()
+        if not os.path.exists(fields[0]):
+            return ["{}:{}: ignored file {} is missing"
+                    .format(self.filename, lineno, fields[0]),
+                    text]