title: Dynamic path for django FileSystemStorage
body: <p>I was trying to save some files using Django FileSystemStorage. My model is as shown below</p>
  
  <pre><code>key_store = FileSystemStorage(
  location='account/files/'+datetime.date.today().isoformat())
  
  
  class Account(models.Model):
      name = models.CharField(max_length=100, null=True, blank=True)
      user = models.ForeignKey(User, related_name='auth_user_account_relation')
      subscription_id = models.CharField(max_length=100, null=True, blank=True)
      info_file = models.FileField(storage=key_store)
  </code></pre>
  
  <p>But when I save an object of this model only the file name is stored in the db.</p>
  
  <p>So when I try to access the path it returns path appended with todays date and not as the uploaded date. 
  ie. If I upload a file on say 09-21-2015 and I try to access the path on the next day it will return 
  <code>account/files/09-22-2015/&lt;file_name&gt;</code> which will be an invalid path.
  So what tweak should be made to store absolute path in db. Or what am I doing wrong here?</p>