consistent install even if installing numpy at the same time?

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One sometimes needs to install numpy before arrow.

File "<string>", line 1, in <module> File "/tmp/pip-install-kixeniwe/stochastic-arrow/setup.py", line 6, in <module>                                                  
        import numpy.distutils.misc_util                                                                                                      
    ModuleNotFoundError: No module named 'numpy'

But pip install is inconsistent! After installing numpy in one virtualenv, you can create another virtualenv and install all requirements at once, including numpy and arrow. (Something must be cached.)

Installing all the requirements at once saves people steps and another way to get fouled up during installation.

Q. Can we fix this in the arrow setup.py?

• Does arrow still need numpy headers now that it uses cython?
• Could it defer calling numpy distlib until after pip has installed numpy?
• How do other packages do it?