Change all "conn = engine.connect()" statements to "with engine.connect() as conn:" in ub.py

Changed all the statements in ub.py to use python context managers so that conn.close() is called automatically.  (https://docs.sqlalchemy.org/en/13/core/connections.html)

cps/ub.py

@@ -474,14 +474,14 @@ def migrate_Database(session):
         ArchivedBook.__table__.create(bind=engine)
     if not engine.dialect.has_table(engine.connect(), "registration"):
         ReadBook.__table__.create(bind=engine)
-        conn = engine.connect()
+        with engine.connect() as conn:
             conn.execute("insert into registration (domain, allow) values('%.%',1)")
         session.commit()
     try:
         session.query(exists().where(Registration.allow)).scalar()
         session.commit()
     except exc.OperationalError:  # Database is not compatible, some columns are missing
-        conn = engine.connect()
+        with engine.connect() as conn:
             conn.execute("ALTER TABLE registration ADD column 'allow' INTEGER")
             conn.execute("update registration set 'allow' = 1")
         session.commit()
@@ -489,14 +489,14 @@ def migrate_Database(session):
         session.query(exists().where(RemoteAuthToken.token_type)).scalar()
         session.commit()
     except exc.OperationalError:  # Database is not compatible, some columns are missing
-        conn = engine.connect()
+        with engine.connect() as conn:
             conn.execute("ALTER TABLE remote_auth_token ADD column 'token_type' INTEGER DEFAULT 0")
             conn.execute("update remote_auth_token set 'token_type' = 0")
         session.commit()
     try:
         session.query(exists().where(ReadBook.read_status)).scalar()
     except exc.OperationalError:
-        conn = engine.connect()
+        with engine.connect() as conn:
             conn.execute("ALTER TABLE book_read_link ADD column 'read_status' INTEGER DEFAULT 0")
             conn.execute("UPDATE book_read_link SET 'read_status' = 1 WHERE is_read")
             conn.execute("ALTER TABLE book_read_link ADD column 'last_modified' DATETIME")
@@ -510,7 +510,7 @@ def migrate_Database(session):
     try:
         session.query(exists().where(Shelf.uuid)).scalar()
     except exc.OperationalError:
-        conn = engine.connect()
+        with engine.connect() as conn:
             conn.execute("ALTER TABLE shelf ADD column 'uuid' STRING")
             conn.execute("ALTER TABLE shelf ADD column 'created' DATETIME")
             conn.execute("ALTER TABLE shelf ADD column 'last_modified' DATETIME")
@@ -525,30 +525,30 @@ def migrate_Database(session):
     # Handle table exists, but no content
     cnt = session.query(Registration).count()
     if not cnt:
-        conn = engine.connect()
+        with engine.connect() as conn:
             conn.execute("insert into registration (domain, allow) values('%.%',1)")
         session.commit()
     try:
         session.query(exists().where(BookShelf.order)).scalar()
     except exc.OperationalError:  # Database is not compatible, some columns are missing
-        conn = engine.connect()
+        with engine.connect() as conn:
             conn.execute("ALTER TABLE book_shelf_link ADD column 'order' INTEGER DEFAULT 1")
         session.commit()
     try:
         create = False
         session.query(exists().where(User.sidebar_view)).scalar()
     except exc.OperationalError:  # Database is not compatible, some columns are missing
-        conn = engine.connect()
+        with engine.connect() as conn:
             conn.execute("ALTER TABLE user ADD column `sidebar_view` Integer DEFAULT 1")
         session.commit()
         create = True
     try:
         if create:
-            conn = engine.connect()
+            with engine.connect() as conn:
                 conn.execute("SELECT language_books FROM user")
             session.commit()
     except exc.OperationalError:
-        conn = engine.connect()
+        with engine.connect() as conn:
             conn.execute("UPDATE user SET 'sidebar_view' = (random_books* :side_random + language_books * :side_lang "
                      "+ series_books * :side_series + category_books * :side_category + hot_books * "
                      ":side_hot + :side_autor + :detail_random)",
@@ -560,7 +560,7 @@ def migrate_Database(session):
     try:
         session.query(exists().where(User.denied_tags)).scalar()
     except exc.OperationalError:  # Database is not compatible, some columns are missing
-        conn = engine.connect()
+        with engine.connect() as conn:
             conn.execute("ALTER TABLE user ADD column `denied_tags` String DEFAULT ''")
             conn.execute("ALTER TABLE user ADD column `allowed_tags` String DEFAULT ''")
             conn.execute("ALTER TABLE user ADD column `denied_column_value` String DEFAULT ''")
@@ -569,7 +569,7 @@ def migrate_Database(session):
     try:
         session.query(exists().where(User.series_view)).scalar()
     except exc.OperationalError:
-        conn = engine.connect()
+        with engine.connect() as conn:
             conn.execute("ALTER TABLE user ADD column `series_view` VARCHAR(10) DEFAULT 'list'")
 
     if session.query(User).filter(User.role.op('&')(constants.ROLE_ANONYMOUS) == constants.ROLE_ANONYMOUS).first() \
@@ -577,11 +577,11 @@ def migrate_Database(session):
         create_anonymous_user(session)
     try:
         # check if one table with autoincrement is existing (should be user table)
-        conn = engine.connect()
+        with engine.connect() as conn:
             conn.execute("SELECT COUNT(*) FROM sqlite_sequence WHERE name='user'")
     except exc.OperationalError:
         # Create new table user_id and copy contents of table user into it
-        conn = engine.connect()
+        with engine.connect() as conn:
             conn.execute("CREATE TABLE user_id (id INTEGER NOT NULL PRIMARY KEY AUTOINCREMENT,"
                      "nickname VARCHAR(64),"
                      "email VARCHAR(120),"
@@ -605,7 +605,7 @@ def migrate_Database(session):
 
     # Remove login capability of user Guest
     try:
-        conn = engine.connect()
+        with engine.connect() as conn:
             conn.execute("UPDATE user SET password='' where nickname = 'Guest' and password !=''")
         session.commit()
     except exc.OperationalError: