title: exception while running bitbake
body: <p>taking my first steps in BitBake using <a href="https://a4z.bitbucket.io/docs/BitBake/guide.html" rel="nofollow noreferrer">this guide</a>, setup works fine until the point when i run <code>bitbake world</code>, where i get this - </p>
  
  <pre><code>    WARNING: python should use 4 spaces indentation, but found tabs in base.bbclass, line 41
  ....
      WARNING: python should use 4 spaces indentation, but found tabs in base.bbclass, line 64
      Parsing recipes: 100% |###########################################################################################################################################################################| Time: 0:00:00
      Parsing of 1 .bb files complete (0 cached, 1 parsed). 1 targets, 0 skipped, 0 masked, 0 errors.
      NOTE: Resolving any missing task queue dependencies
      ERROR: An uncaught exception occurred in runqueue###################################################                                                                                              | ETA:  0:00:00
      Traceback (most recent call last):
        File "/home/ubuntu/bitbake/lib/bb/runqueue.py", line 1508, in RunQueue.execute_runqueue():
                   try:
          &gt;            return self._execute_runqueue()
                   except bb.runqueue.TaskFailure:
        File "/home/ubuntu/bitbake/lib/bb/runqueue.py", line 1428, in RunQueue._execute_runqueue():
                                                                       [43, 967, 4, 3, 1, 5, 3, 7, 13, 1, 2, 1, 1, 246, 35, 1, 38, 1, 35, 2, 338, 204, 142, 3, 3, 37, 244])
          &gt;            if self.rqdata.prepare() == 0:
                           self.state = runQueueComplete
        File "/home/ubuntu/bitbake/lib/bb/runqueue.py", line 1164, in RunQueueData.prepare():
                               todeal.remove(tid)
          &gt;                    self.prepare_task_hash(tid)
  
        File "/home/ubuntu/bitbake/lib/bb/runqueue.py", line 1177, in RunQueueData.prepare_task_hash(tid='/home/ubuntu/Poky/poky/meta-tutorial/recipes-tutorial/first/first_0.1.bb:do_build'):
                   self.runtaskentries[tid].hash = bb.parse.siggen.get_taskhash(taskfn, taskname, procdep, self.dataCaches[mc])
          &gt;        self.runtaskentries[tid].unihash = bb.parse.siggen.get_unihash(taskfn + "." + taskname)
  
        File "/home/ubuntu/bitbake/lib/bb/siggen.py", line 45, in SignatureGenerator.get_unihash(task='/home/ubuntu/Poky/poky/meta-tutorial/recipes-tutorial/first/first_0.1.bb.do_build'):
               def get_unihash(self, task):
          &gt;        return self.taskhash[task]
  
      KeyError: '/home/ubuntu/Poky/poky/meta-tutorial/recipes-tutorial/first/first_0.1.bb.do_build'
  
  
      Summary: There were 13 WARNING messages shown.
      Summary: There were 2 ERROR messages shown, returning a non-zero exit code.
  </code></pre>
  
  <p>and yes - i pulled the latest BitBake from github:</p>
  
  <pre><code>bitbake --version
  BitBake Build Tool Core version 1.40.0
  </code></pre>
  
  <p>what's wrong with my python code?</p>