tweak eval_quoted_string helper function in test_quote_py_str to be compatible with both (old versions of) Python 2.7 & 3.x

Author: boegel

test/framework/easyconfig.py

@@ -2147,10 +2147,13 @@ def eval_quoted_string(quoted_val, val):
             """
             globals = dict()
             try:
-                exec('res = %s' % quoted_val, globals)
+                # this is needlessly complicated because we can't use 'exec' here without potentially running
+                # into a SyntaxError bug in old Python 2.7 versions (for example when running the tests in CentOS 7.9)
+                # cfr. https://stackoverflow.com/questions/4484872/why-doesnt-exec-work-in-a-function-with-a-subfunction
+                edict = {}; eval(compile('res = %s' % quoted_val, '<string>', 'exec'), globals, edict)
             except Exception as e:  # pylint: disable=broad-except
                 self.fail('Failed to evaluate %s (from %s): %s' % (quoted_val, val, e))
-            return globals['res']
+            return edict['res']
 
         def assertEqual_unquoted(quoted_val, val):
             """Assert that evaluating the quoted_val yields the val"""