run-tests: skip tests that require apksigner when running on Java8

The buildserver VM has not been upgraded yet to bullseye, so it is still on
Debian/stretch.  The buildserver VM does not need to run `fdroid update`,
`fdroid signindex`, etc. so this new apksigner requirement should not
affect app builds even though they are stuck on Debian/stretch.

tests/run-tests

@@ -202,6 +202,17 @@ if use_apksigner; then
     grep -F '<application id=' repo/index.xml > /dev/null
 fi
 
+
+#------------------------------------------------------------------------------#
+echo_header "TODO remove once buildserver image is upgraded to bullseye with apksigner"
+
+if java -version 2>&1 | grep -F 1.8.0; then
+    echo "Skipping the rest because they require apksigner 30.0.0+ which does not run on Java8"
+    echo SUCCESS
+    exit
+fi
+
+
 #------------------------------------------------------------------------------#
 echo_header "test UTF-8 metadata"
 

tests/signindex.TestCase

@@ -70,6 +70,8 @@ class SignindexTest(unittest.TestCase):
             signindex.sign_index(str(self.repodir), 'index-v1.json')
 
     def test_signindex(self):
+        if common.find_apksigner({}) is None:  # TODO remove me for buildserver-bullseye
+            self.skipTest('SKIPPING test_signindex, apksigner not installed!')
         os.mkdir('archive')
         metadata = Path('metadata')
         metadata.mkdir()

tests/update.TestCase

@@ -1165,6 +1165,8 @@ class UpdateTest(unittest.TestCase):
 
         fdroidserver.common.options = Options
         config = fdroidserver.common.read_config(fdroidserver.common.options)
+        if 'apksigner' not in config:  # TODO remove me for buildserver-bullseye
+            self.skipTest('SKIPPING test_update_with_AllowedAPKSigningKeys, apksigner not installed!')
         config['repo_keyalias'] = 'sova'
         config['keystorepass'] = 'r9aquRHYoI8+dYz6jKrLntQ5/NJNASFBacJh7Jv2BlI='
         config['keypass'] = 'r9aquRHYoI8+dYz6jKrLntQ5/NJNASFBacJh7Jv2BlI='