make user mobile num nullable if user has email_auth enabled

migrations/versions/0136_user_mobile_nullable.py

@@ -0,0 +1,28 @@
+"""
+
+Revision ID: 0136_user_mobile_nullable
+Revises: 0135_stats_template_usage
+Create Date: 2017-11-08 11:49:05.773974
+
+"""
+from alembic import op
+import sqlalchemy as sa
+from sqlalchemy.sql import column
+from sqlalchemy.dialects import postgresql
+
+revision = '0136_user_mobile_nullable'
+down_revision = '0135_stats_template_usage'
+
+
+def upgrade():
+    op.alter_column('users', 'mobile_number', nullable=True)
+
+    op.create_check_constraint(
+        'ck_users_mobile_or_email_auth',
+        'users',
+        "auth_type = 'email_auth' or mobile_number is not null"
+    )
+
+def downgrade():
+    op.alter_column('users', 'mobile_number', nullable=False)
+    op.drop_constraint('ck_users_mobile_or_email_auth', 'users')