title: TypeError: int() argument must be a string, a bytes-like object or a number, not 'NoneType'
body: <p>i am trying to make a code that print out calendar with some given months and years.
  My code look like this:</p>
  
  <pre><code>#!/usr/bin/python3
  """import calender"""
  
  import calendar
  import datetime
  
  """ begin function """
  
  
  def get_the_first_day_of_the_week(month, year):
      day_of_week = datetime.date(year, month, 1).weekday()
      return
  
  
  def print_out_calender(months, years):
      this_month = int(months)
      this_year = int(years)
      new = get_the_first_day_of_the_week(this_month, this_year)
      new = int(new)
      calendar.setfirstweekday(new)
      calendar.monthcalendar(this_month, this_year)
      return
  
  
  print_out_calender(12, 2017)
  </code></pre>
  
  <p>i expect it to print out matrix of date but i got an error like this:
  Traceback (most recent call last):</p>
  
  <pre><code>  File "./practice12.py", line 25, in &lt;module&gt;
      print_out_calender(12, 2017)
    File "./practice12.py", line 19, in print_out_calender
      new = int(new)
  TypeError: int() argument must be a string, a bytes-like object or a number, not 'NoneType'
  </code></pre>
  
  <p>i am new to python and coding so can somebody tell me why?</p>