[PR #10863/9d0150b2 backport][stable-11] [doc] update requirements for all consul modules/lookups (#10872)

[doc] update requirements for all consul modules/lookups (#10863)

* [doc] update requirements for consul_kv module

python-consul has been unmaintained for a while. It uses a legacy way of passing the Consul token when sending requests. This leads to warning messages in Consul log, and will eventually break communication. Using the maintained py-consul library ensures compatibility to newer Consul versions.

* [doc] replace all python-consul occurrences with py-consul

* [fix] tests and possible pip server errors

* [chore] remove referencce to python-consul in comment

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(cherry picked from commit 9d0150b2c3)

Co-authored-by: Sebastian Damm <SipSeb@users.noreply.github.com>
Co-authored-by: Sebastian Damm <sebastian.damm@pascom.net>

tests/utils/constraints.txt

@@ -27,3 +27,5 @@ redis ; python_version >= '3.6'
 pycdlib < 1.13.0 ; python_version < '3'  # 1.13.0 does not work with Python 2, while not declaring that
 python-daemon <= 2.3.0 ; python_version < '3'
 bcrypt < 4.0.0  # TEMP: restrict to < 4.0.0 since installing 4.0.0 fails on RHEL 8
+py-consul < 1.3.0 ; python_version < '3.8'  # 1.3.0 dropped support for Python 3.5, 3.6, 3.7
+py-consul < 1.5.4 ; python_version < '3.9'  # 1.5.4 dropped support for Python 3.8