Add setuptools

Looks like recent python does not install setuptools, used in drenv
setup.py script. We probably need to switch to more modern library, but
lets first fix the error by installing setuptools. We can look at
modernizing the setup later.

Signed-off-by: Nir Soffer <nsoffer@redhat.com>

requirements.txt

@@ -1,5 +1,6 @@
-pytest
+black
 coverage
 flake8
 pylint
-black
+pytest
+setuptools