Add some error checking when starting Linux daemons.

rattail/daemon.py

@@ -91,6 +91,12 @@ class Daemon(object):
 
         # Start the daemon
         if daemonize:
+            # Make sure the pidfile will be writable.
+            folder = os.path.dirname(self.pidfile)
+            if not os.path.exists(folder):
+                os.makedirs(folder)
+            if not os.access(folder, os.W_OK):
+                raise RuntimeError(u"Cannot write to folder: {0}".format(folder))
             self.daemonize()
         self.run()