Build error installing from pypi

[tykurtz]

Describe the bug For projects that include toppra as a dependency, it is necessary to pre-install numpy and cython . e.g. pip install numpy cython; pip install -r requirements.txt

Some reading material on this issue since it's not unique to toppra

• https://pip.pypa.io/en/stable/reference/pip/#build-system-interface
• https://www.python.org/dev/peps/pep-0518/
• https://stackoverflow.com/a/54138355

To Reproduce

rm -rf ~/.cache/pip
mkvirtualenv --python 3.7 toppra-testing
pip install --upgrade pip
pip install toppra

which returns

    ERROR: Command errored out with exit status 1:
     command: /home/tyler/.virtual_envs/toppra-testing/bin/python -c 'import sys, setuptools, tokenize; sys.argv[0] = '"'"'/tmp/pip-install-2vcf69u8/toppra_6dbedb1d31e145f3bddb098516f7c839/setup.py'"'"'; __file__='"'"'/tmp/pip-install-2vcf69u8/toppra_6dbedb1d31e145f3bddb098516f7c839/setup.py'"'"';f=getattr(tokenize, '"'"'open'"'"', open)(__file__);code=f.read().replace('"'"'\r\n'"'"', '"'"'\n'"'"');f.close();exec(compile(code, __file__, '"'"'exec'"'"'))' egg_info --egg-base /tmp/pip-pip-egg-info-_16s67c0
         cwd: /tmp/pip-install-2vcf69u8/toppra_6dbedb1d31e145f3bddb098516f7c839/
    Complete output (5 lines):
    Traceback (most recent call last):
      File "<string>", line 1, in <module>
      File "/tmp/pip-install-2vcf69u8/toppra_6dbedb1d31e145f3bddb098516f7c839/setup.py", line 3, in <module>
        from Cython.Distutils import build_ext
    ModuleNotFoundError: No module named 'Cython'
    ----------------------------------------
ERROR: Command errored out with exit status 1: python setup.py egg_info Check the logs for full command output.

Expected behavior pip install -r requirements.txt works without pre-installing numpy and cython where requirements.txt includes toppra.

Screenshots If applicable, add screenshots to help explain your problem.

Version Repeatable on pypi as well as locally on origin/develop

[tykurtz]

Hey @hungpham2511 , thanks for merging that fix.

Could we please get a new release? It would make building virtualenvs which include toppra as a dependency much smoother!

[hungpham2511]

Right, let me try to get to release a new version soon. Thanks for nudging!