Workaround setuptools_scm bug for Ubuntu 16.04

"setuptools_scm >=1.8.0, <=1.10.1" had a bug where callables would
crash the installation when installing from an sdist.

Ubuntu 16.04 ships with 1.10.1...

This workaround just noops the pop call that is causing the issue.

see: pypa/setuptools-scm@ff948dcd99

setup.py

@@ -58,6 +58,14 @@ def editable_local_scheme(version):
     }
 
 
+# workaround:
+#  sdist installs with callables were broken between
+#  "setuptools_scm >=1.8, <=1.10.1" and of course ubuntu 16.04 ships
+#  with setuptools_scm==1.10.1 ...
+#  since we're not using "root" we can just noop
+pyusb_scm_version.pop = lambda *_: None
+
+
 setup(
     name='pyusb',
     use_scm_version=pyusb_scm_version,