sql.h not found when installing PyODBC on Heroku
I recently saw this error in Heroku. To fix this problem I took the following steps:

Add Apt File to the root folder, with the following:
unixodbc
unixodbc-dev
python-pyodbc
libsqliteodbc
Commit that
Run heroku buildpacks:clear
Run heroku buildpacks:add --index 1 heroku-community/apt
Push to Heroku

For me the problem was that I previously installed the buildpack for python, which was not needed. By running heroku buildpacks:clearI removed all un-needed buildpacka, then add back the one I needed. So if you do follow these steps be sure to make note of the build packs you need. To view the buildpacks you have run heroku buildpacks before following these steps.
I'm trying to install PyODBC on Heroku, but I get fatal error: sql.h: No such file or directory in the logs when pip runs.  How do I fix this error?