Force distutils to be used instead of falling back to it after trying
setuptools in order to avoid bootstrap issues.

--- pyparsing-2.2.0/setup.py
+++ pyparsing-2.2.0/setup.py
@@ -4,10 +4,7 @@
 
 # Setuptools depends on pyparsing (via packaging) as of version 34, so allow
 # installing without it to avoid bootstrap problems.
-try:
-    from setuptools import setup
-except ImportError:
-    from distutils.core import setup
+from distutils.core import setup
 
 import sys
 import os
