Remove unecessary global declaration in core.py that failed on new flake8 lint. Pinning on paramiko was removed as older versions use pycrypto which is incompatible with Python 3.12. Change-Id: I2811788129fd2b21416d3c64fff870c1542bedc0 Signed-off-by: Myles Penner <myles.penner@canonical.com>