Create string from return value

stdout returns a list of strings.
This needed to be handled.

git_repository.py

@@ -17,8 +17,8 @@ class GitRepository():
         return inst
 
     def get_latest_commit(self):
-        self.system_repository.run_checked('git', 'log', '--oneline', '--format="%s %b"', '-n' + '1')
-        self.latest_commit = self.system_repository.stdout
+        self.system_repository.run_checked('git', 'log', '--oneline', '--format="%s %b"', '-n 1')
+        self.latest_commit = " ".join(self.system_repository.stdout) # returns a list of strings otherwise
 
     def get_release_type_from_latest_commit(self):
         if self.latest_commit is None: