More refactoring of Python code to address Sonar issues (#906)

- Use Path objects for file operations
- Use urllib to sanitize URLs
- Some explicit type conversions
- Consistent regex syntax
- Add rudimentary logging when archive extraction caching fails
- Fixed two cases of the property file creation not being notified in the Flash message
- added doctype and html lang attribute to the web server 502 page

python/web/src/web_utils.py

@@ -240,6 +240,7 @@ def is_bridge_configured(interface):
     Takes (str) interface of a network device being attached.
     Returns a (dict) with (bool) status and (str) msg
     """
+    # TODO: Reduce the nesting of these checks, and streamline how the results are notified
     status = True
     return_msg = ""
     sys_cmd = SysCmds()