Fix migration issues:

- MySQL 5.5 doesn't support the now() call as a default
  - Postgres migration isn't auto-committed, so we have to check if the table exists first

data/migrations/env.py

@@ -5,7 +5,7 @@ import os
 from alembic import context
 from sqlalchemy import engine_from_config, pool
 from logging.config import fileConfig
-from urllib import unquote
+from urllib import unquote, quote
 from peewee import SqliteDatabase
 
 from data.database import all_models, db
@@ -24,6 +24,11 @@ if 'GENMIGRATE' in os.environ:
     else:
         db_uri = 'postgresql://postgres@%s/genschema' % (docker_host_ip)
 
+if 'DB_URI' in os.environ:
+    db_uri = os.environ['DB_URI']
+
+app.config['DB_URI'] = db_uri
+
 config = context.config
 config.set_main_option('sqlalchemy.url', db_uri)
 
@@ -69,7 +74,7 @@ def run_migrations_online():
 
     """
 
-    if isinstance(db.obj, SqliteDatabase) and not 'GENMIGRATE' in os.environ:
+    if isinstance(db.obj, SqliteDatabase) and not 'GENMIGRATE' in os.environ and not 'DB_URI' in os.environ:
         print ('Skipping Sqlite migration!')
         return