Improved coding style in migration environment script.

(Redmine issue: #4230,#3443)

migrations/env.py

+#-------------------------------------------------------------------------------
+# This file is part of Mentat system (https://mentat.cesnet.cz/).
+#
+# Copyright (C) since 2011 CESNET, z.s.p.o (http://www.ces.net/)
+# Use of this source is governed by the MIT license, see LICENSE file.
+#-------------------------------------------------------------------------------
+
+"""
+This module contains environment setup for `Alembic-based <https://alembic.sqlalchemy.org/en/latest/index.html>`__
+database migrations for metadata database ``mentat_main``.
+"""
+
 from __future__ import with_statement
-from alembic import context
-from sqlalchemy import engine_from_config, pool
+
 from logging.config import fileConfig
 import logging
 
-# this is the Alembic Config object, which provides
-# access to the values within the .ini file in use.
-config = context.config
-
-# Interpret the config file for Python logging.
-# This line sets up loggers basically.
-fileConfig(config.config_file_name)
-logger = logging.getLogger('alembic.env')
+from sqlalchemy import engine_from_config, pool
+from alembic import context
 
-# add your model's MetaData object here
-# for 'autogenerate' support
-# from myapp import mymodel
-# target_metadata = mymodel.Base.metadata
 from flask import current_app
-config.set_main_option('sqlalchemy.url',
-                       current_app.config.get('SQLALCHEMY_DATABASE_URI'))
-target_metadata = current_app.extensions['migrate'].db.metadata
 
-# other values from the config, defined by the needs of env.py,
-# can be acquired:
-# my_important_option = config.get_main_option("my_important_option")
-# ... etc.
+# This is the Alembic Config object, which provides access to the values within
+# the .ini file in use.
+CONFIG = context.config
 
+# Interpret the config file for Python logging. This line sets up loggers basically.
+fileConfig(CONFIG.config_file_name)
+LOGGER = logging.getLogger('alembic.env')
 
-def run_migrations_offline():
-    """Run migrations in 'offline' mode.
+# Add your model's MetaData object here for 'autogenerate' support.
+CONFIG.set_main_option(
+    'sqlalchemy.url',
+    current_app.config.get('SQLALCHEMY_DATABASE_URI')
+)
+TARGET_METADATA = current_app.extensions['migrate'].db.metadata
+
+# Other values from the config, defined by the needs of env.py, can be acquired:
+#   my_important_option = config.get_main_option("my_important_option")
+#   ... etc.
 
-    This configures the context with just a URL
-    and not an Engine, though an Engine is acceptable
-    here as well.  By skipping the Engine creation
-    we don't even need a DBAPI to be available.
+def run_migrations_offline():
+    """
+    Run migrations in 'offline' mode.
 
-    Calls to context.execute() here emit the given string to the
-    script output.
+    This configures the context with just a URL and not an Engine, though an
+    Engine is acceptable here as well.  By skipping the Engine creation we don't
+    even need a DBAPI to be available.
 
+    Calls to context.execute() here emit the given string to the script output.
     """
-    url = config.get_main_option("sqlalchemy.url")
-    context.configure(url=url)
+    url = CONFIG.get_main_option("sqlalchemy.url")
+    context.configure(url = url)
 
     with context.begin_transaction():
         context.run_migrations()
 
 
 def run_migrations_online():
-    """Run migrations in 'online' mode.
-
-    In this scenario we need to create an Engine
-    and associate a connection with the context.
+    """
+    Run migrations in 'online' mode.
 
+    In this scenario we need to create an Engine and associate a connection with
+    the context.
     """
 
-    # this callback is used to prevent an auto-migration from being generated
-    # when there are no changes to the schema
-    # reference: http://alembic.zzzcomputing.com/en/latest/cookbook.html
-    def process_revision_directives(context, revision, directives):
-        if getattr(config.cmd_opts, 'autogenerate', False):
+    # This callback is used to prevent an auto-migration from being generated
+    # when there are no changes to the schema.
+    #   reference: http://alembic.zzzcomputing.com/en/latest/cookbook.html
+    def process_revision_directives(ctxt, rev, directives):  # pylint: disable=locally-disabled,unused-argument
+        if getattr(CONFIG.cmd_opts, 'autogenerate', False):
             script = directives[0]
             if script.upgrade_ops.is_empty():
                 directives[:] = []
-                logger.info('No changes in schema detected.')
+                LOGGER.info('No changes in schema detected.')
 
-    engine = engine_from_config(config.get_section(config.config_ini_section),
-                                prefix='sqlalchemy.',
-                                poolclass=pool.NullPool)
+    engine = engine_from_config(
+        CONFIG.get_section(CONFIG.config_ini_section),
+        prefix = 'sqlalchemy.',
+        poolclass = pool.NullPool
+    )
 
     connection = engine.connect()
-    context.configure(connection=connection,
-                      target_metadata=target_metadata,
-                      process_revision_directives=process_revision_directives,
-                      **current_app.extensions['migrate'].configure_args)
+    context.configure(
+        connection = connection,
+        target_metadata = TARGET_METADATA,
+        process_revision_directives = process_revision_directives,
+        **current_app.extensions['migrate'].configure_args
+    )
 
     try:
         with context.begin_transaction():

scripts/sqldb-migrate.py

@@ -9,7 +9,7 @@
 
 
 """
-Utility script for SQL database migrations.
+Utility script for metadata database migrations.
 """