title: bypass validation for form field django
body: <pre><code>            class PostForm(forms.ModelForm):
                  description = forms.CharField(widget=PagedownWidget(show_preview=False))
                  class Meta:
                      model = Post
                      fields = [
                          'title',
                          'image',
                          'video',
                          'description',
                          'public',
                          'tags',
                          ]
  </code></pre>
  
  <p>I am trying to bypass the required field for 'video' but having difficulty doing so. Any suggestions would be appreciated.</p>
  
  <p>this is my models.py, hopefully is should help with knowing how to go on this. </p>
  
  <pre><code>            from django.db import models
  
              from django.db.models import Count, QuerySet, F
              from django.utils import timezone
              from django.conf import settings
              from django.contrib.contenttypes.models import ContentType
              from django.core.urlresolvers import reverse
              from django.db.models.signals import pre_save
              from django.utils.text import slugify
              from markdown_deux import markdown
              from django.utils.safestring import mark_safe
              from embed_video.fields import EmbedVideoField
              from taggit.managers import TaggableManager
  
              from comments.models import Comment
  
              def upload_location(instance, filename):
                  return "%s/%s" %(instance.slug, filename)
  
  
              class Post(models.Model):
                  user = models.ForeignKey(settings.AUTH_USER_MODEL, default=1 )
                  title = models.CharField(max_length=75)
                  slug = models.SlugField(unique=True)
                  video = EmbedVideoField()
                  image = models.ImageField(
                          upload_to=upload_location,
                          null=True,
                          blank=True,
                          width_field="width_field",
                          height_field="height_field")
                  height_field = models.IntegerField(default=0)
                  width_field = models.IntegerField(default=0)
                  description = models.TextField()
                  tags = TaggableManager()
                  public = models.BooleanField(default=False)
                  updated = models.DateTimeField(auto_now_add=False, auto_now=True)
                  created = models.DateTimeField(auto_now_add=True, auto_now=False)
  
  
                  def __str__(self):
                      return self.title
  
                  def get_absolute_url(self):
                      return reverse("posts:detail", kwargs={"slug": self.slug})
  
                  class Meta:
                      ordering = ["-created", "-updated" ]
  
                  def get_markdown(self):
                      description = self.description
                      markdown_text = markdown(description)
                      return mark_safe(markdown_text)
  
                  @property
                  def comments(self):
                      instance = self
                      qs = Comment.objects.filter_by_instance(instance)
                      return qs
  
                  @property
                  def get_content_type(self):
                      instance = self
                      content_type = ContentType.objects.get_for_model(instance.__class__)
                      return content_type
  
  
              def create_slug(instance, new_slug=None):
                      slug = slugify(instance.title)
                      if new_slug is not None:
                          slug = new_slug
                      qs = Post.objects.filter(slug=slug).order_by("-id")
                      exists = qs.exists()
                      if exists:
                          new_slug = "%s-%s" %(slug, qs.first().id)
                          return create_slug(instance, new_slug=new_slug)
                      return slug
  
  
  
              def pre_save_post_receiver(sender, instance, *args, **kwargs):
                  if not instance.slug:
                      instance.slug = create_slug(instance)
  
  
              pre_save.connect(pre_save_post_receiver, sender=Post)
  </code></pre>