I ran into a problem while installing neutron. This error is rather common (as seen through googling) but the solution was hard to find. This is what I found that worked for me. YMMV.
The full error is as follows:
Running setup.py (path:/tmp/pip_build_root/ryu/setup.py) egg_info for package ryu error in ryu setup command: Invalid environment marker: (python_version >= '2.7') Complete output from command python setup.py egg_info: error in ryu setup command: Invalid environment marker: (python_version >= '2.7') ---------------------------------------- Cleaning up... Removing temporary dir /tmp/pip_build_root... Command python setup.py egg_info failed with error code 1 in /tmp/pip_build_root/ryu Exception information: Traceback (most recent call last): File "/usr/lib/python2.7/dist-packages/pip/basecommand.py", line 122, in main status = self.run(options, args) File "/usr/lib/python2.7/dist-packages/pip/commands/install.py", line 278, in run requirement_set.prepare_files(finder, force_root_egg_info=self.bundle, bundle=self.bundle) File "/usr/lib/python2.7/dist-packages/pip/req.py", line 1230, in prepare_files req_to_install.run_egg_info() File "/usr/lib/python2.7/dist-packages/pip/req.py", line 326, in run_egg_info command_desc='python setup.py egg_info') File "/usr/lib/python2.7/dist-packages/pip/util.py", line 715, in call_subprocess % (command_desc, proc.returncode, cwd)) InstallationError: Command python
This was fixed by ensuring that my version of setuptools (not the system package of the same name) was version
18.0.1 or newer.
I got this information from the ryu mailing list.