Issue #20120: Use RawConfigParser for .pypirc parsing, removing support for interpolation unintentionally added with move to Python 3. Behavior no longer does any interpolation in .pypirc files, matching behavior in Python 2.7 and Setuptools 19.0.

Lib/distutils/config.py

@@ -4,7 +4,7 @@ Provides the PyPIRCCommand class, the base class for the command classes
 that uses .pypirc in the distutils.command package.
 """
 import os
-from configparser import ConfigParser
+from configparser import RawConfigParser
 
 from distutils.cmd import Command
 
@@ -53,7 +53,7 @@ class PyPIRCCommand(Command):
             repository = self.repository or self.DEFAULT_REPOSITORY
             realm = self.realm or self.DEFAULT_REALM
 
-            config = ConfigParser()
+            config = RawConfigParser()
             config.read(rc)
             sections = config.sections()
             if 'distutils' in sections:

Misc/NEWS

@@ -10,6 +10,12 @@ Release date: tba
 Core and Builtins
 -----------------
 
+- Issue #20120: Use RawConfigParser for .pypirc parsing,
+  removing support for interpolation unintentionally added
+  with move to Python 3. Behavior no longer does any
+  interpolation in .pypirc files, matching behavior in Python
+  2.7 and Setuptools 19.0.
+
 - Issue #26659: Make the builtin slice type support cycle collection.
 
 - Issue #26718: super.__init__ no longer leaks memory if called multiple times.