go back to py2

test/test.py

diff --git a/test/test.py b/test/test.py
index b3170dc..32cbad2 100755
--- a/test/test.py
+++ b/test/test.py
@@ -226,7 +226,8 @@
   def test_no_32bit(self):
     print('test 32-bit error')
     emsdk_hacked = hack_emsdk('not is_os_64bit()', 'True')
-    failing_call_with_output(f'{sys.executable} {emsdk_hacked} install latest', 'this tool is only provided for 64-bit OSes')
+    failing_call_with_output('%s %s install latest' % (sys.executable, emsdk_hacked),
+                             'this tool is only provided for 64-bit OSes')
     os.remove(emsdk_hacked)
 
   def test_update_no_git(self):