deploy: give useful error if rsync is not installed

fdroidserver/deploy.py

@@ -277,6 +277,12 @@ def update_serverwebroot(serverwebroot, repo_section):
     has a low resolution timestamp
 
     """
+    try:
+        subprocess.run(['rsync', '--version'], capture_output=True, check=True)
+    except Exception as e:
+        raise FDroidException(
+            _('rsync is missing or broken: {error}').format(error=e)
+        ) from e
     rsyncargs = ['rsync', '--archive', '--delete-after', '--safe-links']
     if not options.no_checksum:
         rsyncargs.append('--checksum')

tests/deploy.TestCase

@@ -18,6 +18,7 @@ if localmodule not in sys.path:
 
 import fdroidserver.common
 import fdroidserver.deploy
+from fdroidserver.exception import FDroidException
 from testcommon import TmpCwd, mkdtemp
 
 
@@ -56,6 +57,13 @@ class DeployTest(unittest.TestCase):
         fdroidserver.deploy.update_serverwebroot(str(serverwebroot), 'repo')
         self.assertTrue(dest_apk.is_file())
 
+    @mock.patch.dict(os.environ, clear=True)
+    def test_update_serverwebroot_no_rsync_error(self):
+        os.environ['PATH'] = self.testdir
+        os.chdir(self.testdir)
+        with self.assertRaises(FDroidException):
+            fdroidserver.deploy.update_serverwebroot('serverwebroot', 'repo')
+
     def test_update_serverwebroot_make_cur_version_link(self):
         # setup parameters for this test run
         fdroidserver.deploy.options.no_checksum = True