Add python2.7 support. Yes, that.

setup.py

@@ -1,6 +1,7 @@
 #!/usr/bin/env python
 # -*- coding: utf-8 -*-
 
+from io import open
 from os import path
 from setuptools import setup, find_packages
 

src/pytest_check/check_methods.py

@@ -181,7 +181,7 @@ def log_failure(msg):
         if 'contextlib.py' in file:
             pass
         else:
-            line = f"  {file}, line {line}, in {func}() -> {context}"
+            line = "  {}, line {}, in {}() -> {}".format(file, line, func, context)
             pseudo_trace.append(line)
         level += 1
     pseudo_trace_str = "\n".join(reversed(pseudo_trace))