disable interpolation when parsing config files

Fix pypa#889.

setuptools/dist.py

@@ -438,7 +438,7 @@ def parse_config_files(self, filenames=None):
         and loads configuration.
 
         """
-        _Distribution.parse_config_files(self, filenames=filenames)
+        Distribution_parse_config_files.parse_config_files(self, filenames=filenames)
 
         parse_configuration(self, self.command_options)
         if getattr(self, 'python_requires', None):

setuptools/py36compat.py

@@ -2,6 +2,7 @@
 from distutils.errors import DistutilsOptionError
 from distutils.util import strtobool
 from distutils.debug import DEBUG
+from setuptools.extern import six
 
 
 class Distribution_parse_config_files:
@@ -13,10 +14,10 @@ class Distribution_parse_config_files:
     as implemented in distutils.
     """
     def parse_config_files(self, filenames=None):
-        from configparser import ConfigParser
+        from setuptools.extern.six.moves.configparser import ConfigParser
 
         # Ignore install directory options if we have a venv
-        if sys.prefix != sys.base_prefix:
+        if six.PY3 and sys.prefix != sys.base_prefix:
             ignore_options = [
                 'install-base', 'install-platbase', 'install-lib',
                 'install-platlib', 'install-purelib', 'install-headers',
@@ -33,7 +34,7 @@ def parse_config_files(self, filenames=None):
         if DEBUG:
             self.announce("Distribution.parse_config_files():")
 
-        parser = ConfigParser(interpolation=None)
+        parser = ConfigParser()
         for filename in filenames:
             if DEBUG:
                 self.announce("  reading %s" % filename)
@@ -44,7 +45,7 @@ def parse_config_files(self, filenames=None):
 
                 for opt in options:
                     if opt != '__name__' and opt not in ignore_options:
-                        val = parser.get(section,opt)
+                        val = parser.get(section,opt,raw=True)
                         opt = opt.replace('-', '_')
                         opt_dict[opt] = (filename, val)
 
@@ -69,12 +70,6 @@ def parse_config_files(self, filenames=None):
                     raise DistutilsOptionError(msg)
 
 
-if sys.version_info < (3,):
-    # Python 2 behavior is sufficient
-    class Distribution_parse_config_files:
-        pass
-
-
 if False:
     # When updated behavior is available upstream,
     # disable override here.

setuptools/tests/test_config.py

@@ -288,6 +288,15 @@ def test_classifiers(self, tmpdir):
         with get_dist(tmpdir) as dist:
             assert set(dist.metadata.classifiers) == expected
 
+    def test_no_interpolation(self, tmpdir):
+        fake_env(
+            tmpdir,
+            '[metadata]\n'
+            'description = %(message)s\n'
+        )
+        with get_dist(tmpdir) as dist:
+            assert dist.metadata.description == '%(message)s'
+
 
 class TestOptions: