test/check_exercises.py: improve portability (#1626)

Closes #1625

test/check-exercises.py

@@ -13,10 +13,6 @@
 ALLOW_SKIP = ['alphametics', 'largest-series-product']
 
 
-def python_executable_name():
-    return 'python{}.{}'.format(sys.version_info.major, sys.version_info.minor)
-
-
 def check_assignment(name, test_file):
     # Returns the exit code of the tests
     workdir = tempfile.mkdtemp(name)
@@ -33,7 +29,7 @@ def check_assignment(name, test_file):
                 dst_file.writelines(lines)
         shutil.copyfile(os.path.join(os.path.dirname(test_file), 'example.py'),
                         os.path.join(workdir, '{}.py'.format(example_name)))
-        return subprocess.call([python_executable_name(), test_file_out])
+        return subprocess.call([sys.executable, test_file_out])
     finally:
         shutil.rmtree(workdir)
 
@@ -76,7 +72,7 @@ def main():
                 failures.append('{} (TestFailed)'.format(exercise))
         print('')
 
-    print('TestEnvironment:', python_executable_name().capitalize(), '\n\n')
+    print('TestEnvironment:', sys.executable.capitalize(), '\n\n')
 
     if failures:
         print('FAILURES: ', ', '.join(failures))