I recently purchased a TinyFPGA BX. I thought I would go ahead and install the prerequisite software while I'm waiting on it to arrive. I didn't expect it to go so bad.
It turns out that you need to update your version of Python to Python 3 first. I was able to do that by following the instructions in this post:
The right and wrong way to set Python 3 as default on a Mac
Once I did that, I closed then reopened the terminal. After that, I had to follow the directions on the TinyFPGA site.
However, when it comes to this line:
apio drivers --serial-enable
I had to do something first (I received an error about not being able to write to the .apio folder). Open Finder and then press SHIFT+COMMAND+H to go to your home folder. Then pres SHIFT+COMMAND+. to show hidden folders.
Control+Click on the .apio folder and choose Get Info
You should see the following:

Notice that at the bottom, there is a lock icon. Click this to unlock the settings. Then, give staff and everyone Read & Write permissions on the folder.
Close and re-open terminal.
Then, you should be able to run the commands on the TinyFPGA site without error.