output major version release imminent warning

Updates the library to spew out a warning when the client is initialised
and when an API call is invoked.

This is intentionally annoying and not scoped to stderr to ensure that
if anyone does upgrade, they are quickly notified without any
impediments.

Author: jacobbednarz

CloudFlare/cloudflare.py

@@ -25,6 +25,24 @@
 DEFAULT_GLOBAL_REQUEST_TIMEOUT = 5
 DEFAULT_MAX_REQUEST_RETRIES = 5
 
+MAJOR_VERSION_WARNING = """
+!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!  WARNING  !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
+!!                                                                            !!
+!! You are seeing this warning because you have upgraded to a version that is !!
+!! not intended to be installed.                                              !!
+!!                                                                            !!
+!! This version only exists to catch any accidental upgrades before we        !!
+!! release a major release.                                                   !!
+!!                                                                            !!
+!! You should determine if you need to revert this upgrade and pin to v2.19.* !!
+!! or if you can upgrade to v3.x.                                             !!
+!!                                                                            !!
+!! To see more about upgrading to next major version, please see              !!
+!! https://github.com/cloudflare/python-cloudflare/discussions/191            !!
+!!                                                                            !!
+!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
+"""
+
 class CloudFlare():
     """ A Python interface Cloudflare's v4 API.
 
@@ -50,6 +68,7 @@ class _v4base():
 
         def __init__(self, config):
             """ :meta private: """
+            print(MAJOR_VERSION_WARNING)
 
             self.network = None
             self.config = config
@@ -278,6 +297,7 @@ def do_certauth(self, method, parts, identifiers, params=None, data=None, files=
 
         def _call_network(self, method, headers, parts, identifiers, params, data_str, data_json, files):
             """ Cloudflare v4 API"""
+            print(MAJOR_VERSION_WARNING)
 
             if (method is None) or (parts[0] is None):
                 # should never happen