Switch from inspect.getargspec to inspect.getfullargspec

[domdfcoding]

inspect.getargspec() has been deprecated since 3.0 and has been removed in the 3.11 alphas.

What kind of change does this PR introduce?

• bug fix
• feature
• docs update
• tests/coverage improvement
• refactoring
• other

What is the related issue number (starting with #)

Fixes #1944

What is the current behavior? (You can also link to an open issue here)

An AttributeError is raised when importing cherrypy.

Other information:

Checklist:

• I think the code is well written
• I wrote good commit messages
• I have squashed related commits together after the changes have been approved
• Unit tests for the changes exist
• Integration tests for the changes exist (if applicable)
• I used the same coding conventions as the rest of the project
• The new code doesn't generate linter offenses
• Documentation reflects the changes
• The PR relates to only one subject with a clear title
  and description in grammatically correct, complete sentences

[codecov]

Codecov Report

Merging #1945 (8245a74) into main (a7983fe) will increase coverage by 0.68%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##             main    #1945      +/-   ##
==========================================
+ Coverage   79.34%   80.03%   +0.68%     
==========================================
  Files         105      105              
  Lines       13394    13392       -2     
==========================================
+ Hits        10628    10718      +90     
+ Misses       2766     2674      -92     

[webknjaz]

Nice catch, thanks!

[Safihre]

@webknjaz Will you create a new release of CherryPy? Because Python 3.11Beta is out and we can't use it because CherryPy is not working.

[jaraco]

I cut a release 18.7 in #1966.