requirements.txt has numpy version >= 1.17 even for older bcolz

[maranranu]

I am trying to install bcolz in python2.7 but it fails with an error message

exec(code, globals, locals)
File "/tmp/easy_install-uNq0xS/numpy-1.17.1/setup.py", line 31, in
they've actually been downloaded and installed by setup_requires.
RuntimeError: Python version >= 3.5 required.

Because bcolz requirements.txt has latest numpy version which is incompatible with python2.7.