PYTHON-5393 Make link checking more robust (#2374)

Author: blink1073

doc/changelog.rst

@@ -1700,8 +1700,7 @@ Changes in Version 3.8.0 (2019/04/22)
 -------------------------------------
 
 .. warning:: PyMongo no longer supports Python 2.6. RHEL 6 users should install
-  Python 2.7 or newer from `Red Hat Software Collections
-  <https://developers.redhat.com/products/softwarecollections/overview>`_.
+  Python 2.7 or newer from Red Hat Software Collections.
   CentOS 6 users should install Python 2.7 or newer from `SCL
   <https://wiki.centos.org/AdditionalResources/Repositories/SCL>`_
 

doc/conf.py

@@ -82,7 +82,7 @@
 # Options for link checking
 # The anchors on the rendered markdown page are created after the fact,
 # so those link results in a 404.
-# wiki.centos.org has been flakey.
+# wiki.centos.org has been flaky.
 # sourceforge.net is giving a 403 error, but is still accessible from the browser.
 linkcheck_ignore = [
     "https://github.com/mongodb/specifications/blob/master/source/server-discovery-and-monitoring/server-monitoring.md#requesting-an-immediate-check",
@@ -91,6 +91,9 @@
     r"https://sourceforge.net/",
 ]
 
+# Allow for flaky links.
+linkcheck_retries = 3
+
 # -- Options for extensions ----------------------------------------------------
 autoclass_content = "init"