fix(deps): only require ipaddress on python<3.7 (backport #4300) (#4307)

This is an automatic backport of pull request #4300 done by [Mergify](https://mergify.com).


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Author: mergify[bot]

setup.py

@@ -258,7 +258,7 @@ def get_exts_for(name):
         "pathlib2; python_version<'3.5'",
         "jsonschema",
         "xmltodict>=0.12",
-        "ipaddress",
+        "ipaddress; python_version<'3.7'",
         "envier",
     ]
     + bytecode,