py-alembic: updated to 1.7.7

1.7.7
bug

[bug] [operations]
Fixed issue where using Operations.create_table() in conjunction with a CheckConstraint that referred to table-bound Column objects rather than string expressions would be added to the parent table potentially multiple times, resulting in an incorrect DDL sequence. Pull request courtesy Nicolas CANIART.

[bug] [environment]
The logging.fileConfig() line in env.py templates, which is used to setup Python logging for the migration run, is now conditional on Config.config_file_name not being None. Otherwise, the line is skipped as there is no default logging configuration present.

[bug] [mssql]
Fixed bug where an Operations.alter_column() operation would change a ���NOT NULL��� column to ���NULL��� by emitting an ALTER COLUMN statement that did not specify ���NOT NULL���. (In the absence of ���NOT NULL��� T-SQL was implicitly assuming ���NULL���). An Operations.alter_column() operation that specifies Operations.alter_column.type should also specify include either Operations.alter_column.nullable or Operations.alter_column.existing_nullable to inform Alembic as to whether the emitted DDL should include ���NULL��� or ���NOT NULL���; a warning is now emitted if this is missing under this scenario.

1.7.6
usecase

[usecase] [commands]
Add a new command alembic ensure_version, which will ensure that the Alembic version table is present in the target database, but does not alter its contents. Pull request courtesy Kai Mueller.

bug

[bug] [batch] [regression]
Fixed regression where usage of a with_variant() datatype in conjunction with the existing_type option of op.alter_column() under batch mode would lead to an internal exception.

[bug] [autogenerate]
Implemented support for recognizing and rendering SQLAlchemy ���variant��� types going forward into SQLAlchemy 2.0, where the architecture of ���variant��� datatypes will be changing.
[bug] [autogenerate] [mysql]
Added a rule to the MySQL impl so that the translation between JSON / LONGTEXT is accommodated by autogenerate, treating LONGTEXT from the server as equivalent to an existing JSON in the model.

misc

[mssql]
Removed a warning raised by SQLAlchemy when dropping constraints on MSSQL regarding statement caching.

(adam)