class elevation(models.Model):
rast = models.RasterField(srid=3857)
filename = models.CharField(max_length=120)

def __str__(self):
    return self.rid

from django.contrib.gis.gdal import GDALRaster, SpatialReference
from .models import elevation
def load_elevation(inputfilepath, title, verbose=True):
    raster = GDALRaster(inputfilepath, write=True)
    print(raster, raster.name, raster.width, raster.height, raster.extent, raster.srid)
    # (<Raster object at 0x75c20a8>, u'civildefense/inputs/vvvbxcv.asc', 468, 504, (-918401.3837687642, 4933035.6108884355, -903929.8409687642, 4948620.349288436), None)
    raster.srs = 3857
    print(raster.srs)
    # None
    res = elevation.objects.create(rast=raster, filename=title)

Traceback (most recent call last):
File "C:Python27libsite-packagesdjangocorehandlersexception.py", line 41, in inner
response = get_response(request)
File "C:Python27libsite-packagesdjangocorehandlersbase.py", line 187, in _get_response
response = self.process_exception_by_middleware(e, request)
File "C:Python27libsite-packagesdjangocorehandlersbase.py", line 185, in _get_response
response = wrapped_callback(request, *callback_args, **callback_kwargs)
File "C:UserstestDesktopFaculdadeTesecodedjangogeodjangocivildefenseviews.py", line 138, in loadElevation
  res = load_layer.load_elevation(r'civildefense/inputs/' + title + '.asc', srid, title)
File "C:UserstestDesktopFaculdadeTesecodedjangogeodjangocivildefenseload_layer.py", line 40, in load_elevation
  res = elevation.objects.create(srid=srid, rast=raster, filename=title)
File "C:Python27libsite-packagesdjangodbmodelsmanager.py", line 85, in manager_method
  return getattr(self.get_queryset(), name)(*args, **kwargs)
File "C:Python27libsite-packagesdjangodbmodelsquery.py", line 394, in create
  obj.save(force_insert=True, using=self.db)
File "C:Python27libsite-packagesdjangodbmodelsbase.py", line 808, in save
  force_update=force_update, update_fields=update_fields)
File "C:Python27libsite-packagesdjangodbmodelsbase.py", line 838, in save_base
  updated = self._save_table(raw, cls, force_insert, force_update, using, update_fields)
File "C:Python27libsite-packagesdjangodbmodelsbase.py", line 924, in _save_table
  result = self._do_insert(cls._base_manager, using, fields, update_pk, raw)
File "C:Python27libsite-packagesdjangodbmodelsbase.py", line 963, in _do_insert
  using=using, raw=raw)
File "C:Python27libsite-packagesdjangodbmodelsmanager.py", line 85, in manager_method
  return getattr(self.get_queryset(), name)(*args, **kwargs)
File "C:Python27libsite-packagesdjangodbmodelsquery.py", line 1076, in _insert
  return query.get_compiler(using=using).execute_sql(return_id)
File "C:Python27libsite-packagesdjangodbmodelssqlcompiler.py", line 1111, in execute_sql
  for sql, params in self.as_sql():
File "C:Python27libsite-packagesdjangodbmodelssqlcompiler.py", line 1064, in as_sql
  for obj in self.query.objs
File "C:Python27libsite-packagesdjangodbmodelssqlcompiler.py", line 1003, in prepare_value
  value = field.get_db_prep_save(value, connection=self.connection)
File "C:Python27libsite-packagesdjangocontribgisdbmodelsfields.py", line 182, in get_db_prep_save
  return connection.ops.Adapter(self.get_prep_value(value))
File "C:Python27libsite-packagesdjangocontribgisdbmodelsfields.py", line 244, in get_prep_value
  obj.srid = self.get_srid(obj)
File "C:Python27libsite-packagesdjangocontribgisdbmodelsfields.py", line 171, in get_srid
  srid = obj.srid  # SRID of given geometry.
File "C:Python27libsite-packagesdjangocontribgisgdalrastersource.py", line 233, in srid
  return self.srs.srid
AttributeError: 'NoneType' object has no attribute 'srid'