devel/py-PeachPy: Fix build with setuptools 61.0.0+

With hat:	python

devel/py-PeachPy/files/patch-setup.py

@@ -0,0 +1,11 @@
+--- setup.py.orig	2018-02-25 10:20:32 UTC
++++ setup.py
+@@ -35,7 +35,7 @@ class GenerateInstructions(Command):
+     def run(self):
+         # package_dir may be None, in that case use the current directory.
+         import os
+-        if self.distribution.package_dir is None:
++        if not self.distribution.package_dir:
+             src_dir = os.getcwd()
+         else:
+             src_dir = os.path.abspath(self.distribution.package_dir[""])