Be more liberal with Depends-On: parsing

I just spent quite a while debugging only to realise I'd written
"Depends-On:  https://" (note the two spaces...).

This gets passed to urlparse.parse.urlparse() which does not handle
leading spaces; thus the return is considered invalid and the
Depends-On gets silently ignored.

It seems we should just be liberal with leading and trailing space
around Depends-On: lines.  This strips the results to acheive this,
and adds a small unit-test to cover this.

Change-Id: Iddd8363580fb2fefd99d4783fc90f68f34f0c949

tests/unit/test_dependson.py

@@ -0,0 +1,47 @@
+# Copyright 2021 Red Hat
+#
+# Licensed under the Apache License, Version 2.0 (the "License"); you may
+# not use this file except in compliance with the License. You may obtain
+# a copy of the License at
+#
+#      http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+# WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
+# License for the specific language governing permissions and limitations
+# under the License.
+
+# NOTE(ianw): 2021-08-30 we are testing whitespace things that trigger
+# flake8, for now there is no way to turn of specific tests on a
+# per-file basis.
+
+# flake8: noqa
+
+import textwrap
+
+from zuul.lib.dependson import find_dependency_headers
+
+from tests.base import BaseTestCase
+
+
+class TestDependsOnParsing(BaseTestCase):
+
+    def test_depends_on_parsing(self):
+        msg = textwrap.dedent('''\
+        This is a sample review subject
+
+        Review text
+
+        Depends-On:https://this.is.a.url/1
+        Depends-On: https://this.is.a.url/2  
+        Depends-On:    https://this.is.a.url/3
+        Depends-On:	  https://this.is.a.url/4	
+        ''')
+        r = find_dependency_headers(msg)
+
+        self.assertListEqual(r,
+                             ['https://this.is.a.url/1',
+                              'https://this.is.a.url/2',
+                              'https://this.is.a.url/3',
+                              'https://this.is.a.url/4'])

zuul/lib/dependson.py

@@ -15,7 +15,7 @@
 import re
 
 
-DEPENDS_ON_RE = re.compile(r"^Depends-On: (.*?)\s*$",
+DEPENDS_ON_RE = re.compile(r"^Depends-On:(.*?)\s*$",
                            re.MULTILINE | re.IGNORECASE)
 
 
@@ -25,5 +25,5 @@ def find_dependency_headers(message):
     for match in DEPENDS_ON_RE.findall(message):
         if match in dependencies:
             continue
-        dependencies.append(match)
+        dependencies.append(match.strip())
     return dependencies