add docstring and logging to Database.__migrate method

database.py

@@ -11,7 +11,7 @@ class Database:
     """Implement interaction with the database."""
 
     def __init__(self, dsn: str, log: Logger) -> None:
-        """Create a database file if not exists."""
+        """Create a database if not exists."""
         self.log: Logger = log
         self.log.debug('Database.__init__(DSN=\'%s\')', dsn)
         self.conn: connection = psycopg2.connect(dsn)
@@ -158,6 +158,8 @@ class Database:
         self.conn.commit()
 
     def __migrate(self, dsn: str) -> None:
+        """Migrate or initialize database shema"""
+        self.log.debug(f'Database.__migrate(dsn={dsn})')
         backend = get_backend(dsn)
         migrations = read_migrations('./migrations')