new_contents: """audit_event_data_field_non_nullable
  
  Revision ID: 930
  Revises: 920
  Create Date: 2017-06-19 11:31:56.252791
  
  """
  
  # revision identifiers, used by Alembic.
  revision = '930'
  down_revision = '920'
  
  from alembic import op
  import sqlalchemy as sa
  from sqlalchemy.dialects import postgresql
  
  def upgrade():
      op.alter_column(
          'audit_events',
          'data',
          existing_type=postgresql.JSON(astext_type=sa.Text()),
          nullable=False,
      )
  
  
  def downgrade():
      op.alter_column(
          'audit_events',
          'data',
          existing_type=postgresql.JSON(astext_type=sa.Text()),
          nullable=True,
      )
  
subject: add migration 930: audit_event_data_field_non_nullable