title: A field with precision 10, scale 2 must round to an absolute value less than 10^8
body: <p>I have a django-field <code>total_price</code> in <code>postgres</code> database version <code>9.3.11</code>.</p>
  <p>Here is the code:</p>
  <p><code>total_value = models.DecimalField(decimal_places=100, default=0, max_digits=300)</code></p>
  <p>I want to convert it to proper 2 decimal place. So I wrote this:</p>
  <p><code>total_value = models.DecimalField(decimal_places=2, default=0, max_digits=10)</code></p>
  <h2>My migration file</h2>
  <pre><code># -*- coding: utf-8 -*-
  from __future__ import unicode_literals
  from django.db import models, migrations
  
  class Migration(migrations.Migration):
  
      dependencies = [
          ('my_table', '0040_my_table_skipped'),
      ]
  
      operations = [
          migrations.AlterField(
              model_name='my_table',
              name='total_value',
              field=models.DecimalField(default=0, 
                                        max_digits=10, 
                                        decimal_places=2),
          ),
      ]
  
  </code></pre>
  <p>When I run command <code>python manage.py migrate</code></p>
  <p>I get an error from postgresql:</p>
  <p><code>A field with precision 10, scale 2 must round to an absolute value less than 10^8.</code></p>