Require setuptools>=17.1 in setup.py. Ref https://github.com/GNS3/gns3-server/issues/1751

This is to support environmental markers.
https://github.com/pypa/setuptools/blob/master/CHANGES.rst#171

setup.py

@@ -62,6 +62,7 @@ setup(
     zip_safe=False,
     platforms="any",
     python_requires='>=3.5.3',
+    setup_requires=["setuptools>=17.1"],
     classifiers=[
         "Development Status :: 5 - Production/Stable",
         "Environment :: Console",