title: Unable to Start Scheduler
body: <p>I am new to Python and trying to install Airflow in my Mac, by following this <a href="https://stlong0521.github.io/20161023%20-%20Airflow.html" rel="nofollow noreferrer">tutorial</a></p>
  <p>While these two commands work fine:</p>
  <pre><code>$ airflow initdb
  $ airflow webserver -p 8080
  </code></pre>
  <p>The scheduler command (airflow scheduler) throws the following error:</p>
  <pre><code> [2020-02-18 13:18:09,012] {scheduler_job.py:1382} ERROR - Exception when executing execute_helper Traceback (most recent call last):
  
    File &quot;/Users/mac/Workspace/airflow/airflow_venv/lib/python3.8/site-packages/airflow/jobs/scheduler_job.py&quot;, line 1380, in _execute
      self._execute_helper()
  
    File &quot;/Users/mac/Workspace/airflow/airflow_venv/lib/python3.8/site-packages/airflow/jobs/scheduler_job.py&quot;, line 1413, in _execute_helper
      self.processor_agent.start()
  
    File &quot;/Users/mac/Workspace/airflow/airflow_venv/lib/python3.8/site-packages/airflow/utils/dag_processing.py&quot;, line 554, in start
      self._process.start()
  
    File &quot;/Library/Frameworks/Python.framework/Versions/3.8/lib/python3.8/multiprocessing/process.py&quot;, line 121, in start
      self._popen = self._Popen(self)
  
    File &quot;/Library/Frameworks/Python.framework/Versions/3.8/lib/python3.8/multiprocessing/context.py&quot;, line 224, in _Popen
      return _default_context.get_context().Process._Popen(process_obj)
  
    File &quot;/Library/Frameworks/Python.framework/Versions/3.8/lib/python3.8/multiprocessing/context.py&quot;, line 283, in _Popen
      return Popen(process_obj)
  
    File &quot;/Library/Frameworks/Python.framework/Versions/3.8/lib/python3.8/multiprocessing/popen_spawn_posix.py&quot;, line 32, in __init__
      super().__init__(process_obj)
  
    File &quot;/Library/Frameworks/Python.framework/Versions/3.8/lib/python3.8/multiprocessing/popen_fork.py&quot;, line 19, in __init__
      self._launch(process_obj)
  
    File &quot;/Library/Frameworks/Python.framework/Versions/3.8/lib/python3.8/multiprocessing/popen_spawn_posix.py&quot;, line 47, in _launch
      reduction.dump(process_obj, fp)
  
    File &quot;/Library/Frameworks/Python.framework/Versions/3.8/lib/python3.8/multiprocessing/reduction.py&quot;, line 60, in dump
      ForkingPickler(file, protocol).dump(obj)
  
  AttributeError: Can't pickle local object 'SchedulerJob._execute.&lt;locals&gt;.processor_factory'
  
  [2020-02-18 13:18:09,035] {helpers.py:322} INFO - Sending Signals.SIGTERM to GPID None
  
  Traceback (most recent call last):    File &quot;/Users/mac/Workspace/airflow/airflow_venv/bin/airflow&quot;, line 37, in &lt;module&gt;
      args.func(args)    File &quot;/Users/mac/Workspace/airflow/airflow_venv/lib/python3.8/site-packages/airflow/utils/cli.py&quot;, line 75, in wrapper
      return f(*args, **kwargs)    File &quot;/Users/mac/Workspace/airflow/airflow_venv/lib/python3.8/site-packages/airflow/bin/cli.py&quot;, line 1040, in scheduler
      job.run()    File &quot;/Users/mac/Workspace/airflow/airflow_venv/lib/python3.8/site-packages/airflow/jobs/base_job.py&quot;, line 221, in run
      self._execute()    File &quot;/Users/mac/Workspace/airflow/airflow_venv/lib/python3.8/site-packages/airflow/jobs/scheduler_job.py&quot;, line 1384, in _execute
      self.processor_agent.end()    File &quot;/Users/mac/Workspace/airflow/airflow_venv/lib/python3.8/site-packages/airflow/utils/dag_processing.py&quot;, line 707, in end
      reap_process_group(self._process.pid, log=self.log)    File &quot;/Users/mac/Workspace/airflow/airflow_venv/lib/python3.8/site-packages/airflow/utils/helpers.py&quot;, line 324, in reap_process_group
      signal_procs(sig)    File &quot;/Users/mac/Workspace/airflow/airflow_venv/lib/python3.8/site-packages/airflow/utils/helpers.py&quot;, line 293, in signal_procs
      os.killpg(pgid, sig)
  
  TypeError: an integer is required (got type NoneType)
  </code></pre>