title: build_attrs() got an unexpected keyword argument 'id'
body: <p>I am trying to get date input with month and year drop-down menus. 
  I am using a widget from django snippet.</p>
  
  <p>About the widget: 
  A Widget that splits date input into two  boxes for month and year,
  with 'day' defaulting to the first of the month.</p>
  
  <p>Here's the code of the widget</p>
  
  <pre><code>import datetime
  import re
  from six import string_types
  from django.forms.widgets import Widget, Select
  from django.utils.dates import MONTHS
  from django.utils.safestring import mark_safe
  
  __all__ = ('MonthYearWidget',)
  
  RE_DATE = re.compile(r'(\d{4})-(\d\d?)-(\d\d?)$')
  
  
  class MonthYearWidget(Widget):
      """
      A Widget that splits date input into two &lt;select&gt; boxes for month and year,
      with 'day' defaulting to the first of the month.
  
      Based on SelectDateWidget, in
  
      django/trunk/django/forms/extras/widgets.py
  
  
      """
      none_value = (0, '---')
      month_field = '%s_month'
      year_field = '%s_year'
  
      def __init__(self, attrs=None, years=None, required=True):
          # years is an optional list/tuple of years to use in the "year" select box.
          self.attrs = attrs or {}
          self.required = required
          if years:
              self.years = years
          else:
              this_year = datetime.date.today().year
              self.years = range(this_year, this_year+10)
  
      def render(self, name, value, attrs=None):
          try:
              year_val, month_val = value.year, value.month
          except AttributeError:
              year_val = month_val = None
              if isinstance(value, string_types):
                  match = RE_DATE.match(value)
                  if match:
                      year_val, month_val, day_val = [int(v) for v in match.groups()]
  
          output = []
  
          if 'id' in self.attrs:
              id_ = self.attrs['id']
          else:
              id_ = 'id_%s' % name
  
          month_choices = list(MONTHS.items())
          if not (self.required and value):
              month_choices.append(self.none_value)
          month_choices.sort()
          local_attrs = self.build_attrs(id=self.month_field % id_)
          s = Select(choices=month_choices)
          select_html = s.render(self.month_field % name, month_val, local_attrs)
          output.append(select_html)
  
          year_choices = [(i, i) for i in self.years]
          if not (self.required and value):
              year_choices.insert(0, self.none_value)
          local_attrs['id'] = self.year_field % id_
          s = Select(choices=year_choices)
          select_html = s.render(self.year_field % name, year_val, local_attrs)
          output.append(select_html)
  
          return mark_safe(u'\n'.join(output))
  
      def id_for_label(self, id_):
          return '%s_month' % id_
      id_for_label = classmethod(id_for_label)
  
      def value_from_datadict(self, data, files, name):
          y = data.get(self.year_field % name)
          m = data.get(self.month_field % name)
          if y == m == "0":
              return None
          if y and m:
              return '%s-%s-%s' % (y, m, 1)
          return data.get(name, None)
  </code></pre>
  
  <p>I am getting this errror in my browser</p>
  
  <pre><code>TypeError: build_attrs() got an unexpected keyword argument 'id'
  </code></pre>
  
  <p>My python version is 3.7.0 and Django version is 2.0.7 </p>
  
  <p>How to get rid of this error?</p>