Improve clipboard masking

[victorskl]

• address lgtm alert - https://lgtm.com/projects/g/victorskl/yawsso/alerts/?mode=list
• https://cwe.mitre.org/data/definitions/312.html
• https://cwe.mitre.org/data/definitions/359.html
• https://cwe.mitre.org/data/definitions/532.html

[victorskl]

• ditto CodeQL report https://github.com/victorskl/yawsso/pull/63/checks?check_run_id=7058125157

[victorskl]

Improvement made since 1.0.0rc1. User test avail with pip install -U yawsso==1.0.0rc2