In case it helps someone else:
I also ran into issues related to installing/building
For me, the fix was to install the python-dev library.
$ sudo apt install python-dev
$ sudo apt install python3-dev
$ sudo apt install python3.6-dev
Then I could painlessly install
$ pipenv install fastai
I would highly recommend checking out
pipenv as a modern alternative to
conda, plus I believe
pipenv is now actually maintained by PyPA. Besides automatically creating and switching virtual environments for you,
pipenv also provides a more mature requirements management and “locking” system similar to
npm — including python version requirements — and is probably a little more portable (I never had success using conda’s
environment.yml across 2 different machines), though you may need to
rm Pipfile.lock; pipenv install on a different system, due to the system-specific nature of python dependencies.