Fix --multibuild-package option handling in do_sendsysrq

Concatenating a str and a list does not work.

osc/commandline.py

@@ -6903,9 +6903,10 @@ Please submit there instead, or use --nodevelproject to force direct submission.
             arch = args[3]
             sysrq = args[4]
 
+        packages = [package]
         if opts.multibuild_package:
-            package = package + ":" + opts.multibuild_package
-
+            packages = ['%s:%s' % (package, flavor) for flavor in opts.multibuild_package]
+        for package in packages:
             print(cmdbuild(apiurl, 'sendsysrq', project, package, arch, repo, None, sysrq))
 
     @cmdln.option('-a', '--arch', metavar='ARCH',