Do not interpolate values from tox --showconfig (tox-dev#1585)

Author: Albin Vass

CONTRIBUTORS

@@ -1,3 +1,4 @@
+Albin Vass
 Alex Grönholm
 Alexander Loechel
 Alexander Schepanovski

docs/changelog/1585.bugfix.rst

@@ -0,0 +1 @@
+``tox --showconfig`` no longer tries to interpolate '%' signs.

src/tox/session/commands/show_config.py

@@ -19,7 +19,7 @@
 
 
 def show_config(config):
-    parser = configparser.ConfigParser()
+    parser = configparser.RawConfigParser()
 
     if not config.envlist_explicit or reporter.verbosity() >= reporter.Verbosity.INFO:
         tox_info(config, parser)

tests/unit/session/test_show_config.py

@@ -89,6 +89,21 @@ def test_showconfig(cmd, setup_mixed_conf, args, expected):
     assert found_sections == expected
 
 
+def test_showconfig_interpolation(cmd, initproj):
+    initproj(
+        "no_interpolation",
+        filedefs={
+            "tox.ini": """
+        [tox]
+        envlist = %s
+        [testenv:%s]
+        commands = python -c "print('works')"
+        """
+        },
+    )
+    load_config(("--showconfig",), cmd)
+
+
 def test_config_specific_ini(tmpdir, cmd):
     ini = tmpdir.ensure("hello.ini")
     output = load_config(("-c", ini, "--showconfig"), cmd)