Support comments in whitelist files

We already support comments in blacklist files. we should
do the same for whitelist files as well.

Change-Id: I5ad0c113cdb04dd1bdaa4d8bfdd1a3ab169fb0af

os_testr/os_testr.py

@@ -132,7 +132,14 @@ def path_to_regex(path):
 
 
 def get_regex_from_whitelist_file(file_path):
-    return '|'.join(open(file_path).read().splitlines())
+    lines = []
+    for line in open(file_path).read().splitlines():
+        split_line = line.strip().split('#')
+        # Before the # is the regex
+        line_regex = split_line[0].strip()
+        if line_regex:
+            lines.append(line_regex)
+    return '|'.join(lines)
 
 
 def construct_regex(blacklist_file, whitelist_file, regex, print_exclude):

os_testr/tests/test_os_testr.py

@@ -144,6 +144,18 @@ class TestConstructRegex(base.TestCase):
             result,
             "^((?!fake_regex_3|fake_regex_2|fake_regex_1|fake_regex_0).)*$")
 
+    def test_whitelist_regex_with_comments(self):
+        whitelist_file = six.StringIO()
+        for i in range(4):
+            whitelist_file.write('fake_regex_%s # A Comment\n' % i)
+        whitelist_file.seek(0)
+        with mock.patch('six.moves.builtins.open',
+                        return_value=whitelist_file):
+            result = os_testr.construct_regex(None, 'fake_path', None, False)
+        self.assertEqual(
+            result,
+            "fake_regex_0|fake_regex_1|fake_regex_2|fake_regex_3")
+
     def test_blacklist_regex_without_comments(self):
         blacklist_file = six.StringIO()
         for i in range(4):