MAI: on Python 3, use importlib instead of imp

because the module `imp` has been deprecated since
Python version 3.4 [1].

[1] https://docs.python.org/3.9/library/imp.html

run_tests.py

@@ -7,7 +7,8 @@
 """
 from __future__ import absolute_import
 from __future__ import print_function
-import imp
+# import imp  # inline
+# import importlib  # inline
 import sys
 import os.path
 
@@ -81,8 +82,13 @@
         except ValueError:
             pass
     try:
-        modtuple = imp.find_module("polytope", sys.path)
-        imp.load_module("polytope", *modtuple)
+        if sys.version_info.major == 2:
+            import imp
+            modtuple = imp.find_module("polytope", sys.path)
+            imp.load_module("polytope", *modtuple)
+        else:
+            import importlib
+            importlib.import_module('polytope')
     except ImportError:
         if require_nonlocaldir_polytope:
             raise ImportError(

setup.py

@@ -4,10 +4,12 @@
 from __future__ import print_function
 from __future__ import unicode_literals
 
-import imp
+# import imp  # inline
+# import importlib  # inline
 import os
 from setuptools import setup
 import subprocess
+import sys
 
 
 classifiers = [
@@ -94,8 +96,17 @@ def run_setup():
             f.write(commit_hash_header + '\n')
             f.write(sha1 + '\n')
     # Import polytope/version.py without importing polytope
-    version = imp.load_module('version',
-                              *imp.find_module('version', ['polytope']))
+    if sys.version_info.major == 2:
+        import imp
+        version = imp.load_module('version',
+                                  *imp.find_module('version', ['polytope']))
+    else:
+        import importlib.util
+        spec = importlib.util.spec_from_file_location(
+            'version', 'polytope/version.py')
+        version = importlib.util.module_from_spec(spec)
+        sys.modules['version'] = version
+        spec.loader.exec_module(version)
     polytope_version = version.version
     setup(
         name='polytope',