Update gunicorn requirement from <20.0,>=19.9.0 to >=19.9.0,<21.0

[dependabot]

Updates the requirements on gunicorn to permit the latest version.

Release notes

Sourced from gunicorn's releases.

20.1.0

• document WEB_CONCURRENCY is set by, at least, Heroku
• capture peername from accept: Avoid calls to getpeername by capturing the peer name returned by accept
• log a warning when a worker was terminated due to a signal
• fix tornado usage with latest versions of Django
• add support for python -m gunicorn
• fix systemd socket activation example
• allows to set wsgi application in configg file using wsgi_app
• document --timeout = 0
• always close a connection when the number of requests exceeds the max requests
• Disable keepalive during graceful shutdown
• kill tasks in the gthread workers during upgrade
• fix latency in gevent worker when accepting new requests
• fix file watcher: handle errors when new worker reboot and ensure the list of files is kept
• document the default name and path of the configuration file
• document how variable impact configuration
• document the $PORT environment variable
• added milliseconds option to request_time in access_log
• added PIP requirements to be used for example
• remove version from the Server header
• fix sendfile: use socket.sendfile instead of os.sendfile
• reloader: use absolute path to prevent empty to prevent0 InotifyError when a file is added to the working directory
• Add --print-config option to print the resolved settings at startup.
• remove the --log-dict-config CLI flag because it never had a working format (the logconfig_dict setting in configuration files continues to work)

** Breaking changes **

• minimum version is Python 3.5
• remove version from the Server header

** Documentation **

** Others **

• miscellaneous changes in the code base to be a better citizen with Python 3
• remove dead code
• fix documentation generation

Commits

• 61ccfd6 bump to 20.1.0
• d1f0f11 fix inline code syntax in news
• f87882e add an empty line in news.rst
• 7a79808 update changeslog
• 6fd97b9 Document that WEB_CONCURRENCY is set by, at least, Heroku
• dad99a1 Update gunicorn_ext.py
• 3273492 Improve settings documentation
• 86eac4c Merge pull request #2479 from benoitc/capture-peer-name
• 03c642e Merge pull request #2480 from kofrezo/update_docs_install
• a4407ab Default to Python 3 version of gunicorn in Stretch
• Additional commits viewable in compare view

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[sonarqubecloud]

Kudos, SonarCloud Quality Gate passed!   

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[sonarqubecloud]

Kudos, SonarCloud Quality Gate passed!   

0 Bugs
0 Vulnerabilities
0 Security Hotspots
0 Code Smells

No Coverage information
No Duplication information

[sonarqubecloud]

Kudos, SonarCloud Quality Gate passed!   

0 Bugs
0 Vulnerabilities
0 Security Hotspots
0 Code Smells

No Coverage information
No Duplication information

[codecov-commenter]

Codecov Report

Merging #822 (181e649) into develop (7e9f11a) will increase coverage by 10.55%.
The diff coverage is n/a.

❗ Current head 181e649 differs from pull request most recent head 0b15962. Consider uploading reports for the commit 0b15962 to get more accurate results

@@             Coverage Diff              @@
##           develop     #822       +/-   ##
============================================
+ Coverage    46.33%   56.89%   +10.55%     
============================================
  Files          195      129       -66     
  Lines         7059     1965     -5094     
  Branches       522      522               
============================================
- Hits          3271     1118     -2153     
+ Misses        3684      743     -2941     
  Partials       104      104               

see 66 files with indirect coverage changes

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