Allow using % character in convert2rhel.ini

Whenever a user entered the % character in the convert2rhel.ini config
file, such as in the RHSM password, convert2rhel failed with an error:

configparser.InterpolationSyntaxError: '%' must be followed by '%' or '(', found: "%<STRING>"

The solution is to disable interpreting the % character as a sign for
string replacement.

Related: https://access.redhat.com/solutions/7107977

Author: bocekm

convert2rhel/toolopts/config.py

@@ -20,6 +20,7 @@
 import copy
 import logging
 import os
+from sys import version_info
 
 import six
 
@@ -151,7 +152,14 @@ def _parse_options_from_config(self, paths):
             them.
         :type paths: list[str]
         """
-        config_file = configparser.ConfigParser()
+
+        # The reason for using the RawConfigParser and ConfigParser with interpolation set to None is to prevent
+        # interpreting % as a sign for string replacement. This interpolation feature would cause convert2rhel to fail
+        # if the user enters the % character in the config file, for example in the RHSM password.
+        if version_info.major < 3:
+            config_file = configparser.RawConfigParser()
+        else:
+            config_file = configparser.ConfigParser(interpolation=None)
         found_opts = {}
 
         for path in reversed(paths):

convert2rhel/unit_tests/toolopts/config_test.py

@@ -86,9 +86,9 @@ def test_options_from_config_files_invalid_head_and_options(self, content, expec
             (
                 """\
 [subscription_manager]
-password = correct_password
+password = %correct_password%
                 """,
-                {"password": "correct_password"},
+                {"password": "%correct_password%"},
             ),
             (
                 """\