use backported importlib.resources on older versions of python

Author: krachyon

setup.py

@@ -16,6 +16,7 @@
 
     packages=find_packages(exclude=['tests.*', 'tests']),
     install_requires=[
+        'importlib-resources',
         'numpy>=1.14',
         'matplotlib',
         'scipy',

tests/test_access_resources.py

@@ -1,4 +1,7 @@
-from importlib.resources import read_text, contents, files
+try:
+    from importlib.resources import read_text, contents, files  # type:ignore
+except ModuleNotFoundError:
+    from importlib_resources import read_text, contents, files  # type:ignore
 from unittest import TestCase
 import mascado.resources as res