Issue #22450: Use "Accept: */*" in the default headers for urllib

Lib/urllib.py

@@ -138,7 +138,7 @@ class URLopener:
         self.key_file = x509.get('key_file')
         self.cert_file = x509.get('cert_file')
         self.context = context
-        self.addheaders = [('User-Agent', self.version)]
+        self.addheaders = [('User-Agent', self.version), ('Accept', '*/*')]
         self.__tempfiles = []
         self.__unlink = os.unlink # See cleanup()
         self.tempcache = None

Misc/NEWS

@@ -47,6 +47,10 @@ Library
 - Issue #27570: Avoid zero-length memcpy() etc calls with null source
   pointers in the "ctypes" and "array" modules.
 
+- Issue #22450: urllib now includes an "Accept: */*" header among the
+  default headers.  This makes the results of REST API requests more
+  consistent and predictable especially when proxy servers are involved.
+
 - lib2to3.pgen3.driver.load_grammar() now creates a stable cache file
   between runs given the same Grammar.txt input regardless of the hash
   randomization setting.