tests: Fix top_dir test

The top_dir test is failing on newer versions of python because it
requires that parsing be able to be done on the test host, which some
really old versions simply cannot do. Only run the test if the is
possible, and bump up Ubuntu 18.04 to test on Yocto 3.1

ci/test.py

@@ -58,6 +58,24 @@ def wrapper(self, *args, **kwargs):
     return decorator
 
 
+def minPokyVer(major, minor):
+    def ver_str(major, minor):
+        return "%d.%d" % (major, minor)
+
+    def decorator(func):
+        def wrapper(self, *args, **kwargs):
+            if self.pokyver < (major, minor):
+                self.skipTest(
+                    "Test cannot be used with poky version < %s (using %s)"
+                    % (ver_str(major, minor), ver_str(*self.pokyver))
+                )
+            return func(self, *args, **kwargs)
+
+        return wrapper
+
+    return decorator
+
+
 built_images = set()
 
 
@@ -1052,6 +1070,7 @@ def test_templateconf_rel(self):
         )
         self.assertEqual(s, test_string)
 
+    @minPokyVer(3, 1)
     def test_top_dir(self):
         # Verify that the TOPDIR reported by bitbake in pyrex is the same as
         # the one reported by bitbake outside of pyrex
@@ -1179,28 +1198,28 @@ class PyrexImageType_oetest(PyrexImageType_oe):
 TEST_IMAGES = (
     ("ubuntu-14.04-base", (2, 6)),
     ("ubuntu-16.04-base", (2, 6)),
-    ("ubuntu-18.04-base", (2, 6)),
+    ("ubuntu-18.04-base", (3, 1)),
     ("ubuntu-20.04-base", (3, 1)),
     ("ubuntu-22.04-base", (4, 0)),
     ("ubuntu-14.04-oe", (2, 6)),
     ("ubuntu-16.04-oe", (2, 6)),
-    ("ubuntu-18.04-oe", (2, 6)),
+    ("ubuntu-18.04-oe", (3, 1)),
     ("ubuntu-20.04-oe", (3, 1)),
     ("ubuntu-22.04-oe", (4, 0)),
     ("ubuntu-14.04-oegarmin", (2, 6)),
     ("ubuntu-16.04-oegarmin", (2, 6)),
-    ("ubuntu-18.04-oegarmin", (2, 6)),
+    ("ubuntu-18.04-oegarmin", (3, 1)),
     ("ubuntu-20.04-oegarmin", (3, 1)),
     ("ubuntu-22.04-oegarmin", (4, 0)),
-    ("ubuntu-18.04-oetest", (2, 6)),
+    ("ubuntu-18.04-oetest", (3, 1)),
     ("ubuntu-20.04-oetest", (3, 1)),
 )
 
 
 def add_image_tests():
     self = sys.modules[__name__]
     for provider in PROVIDERS:
-        for (image, pokyver) in TEST_IMAGES:
+        for image, pokyver in TEST_IMAGES:
             (_, _, image_type) = image.split("-")
 
             parent = getattr(self, "PyrexImageType_" + image_type)