Cannot invoke any CLI commands after installing python environment
### Problem
After [installing](https://meltano.com/docs/installation.html#local-installation) `meltano` locally you cannot invoke any `meltano` commands.
~~This affects the latest macOS version (10.15) which now defaults to [`zsh`](https://en.wikipedia.org/wiki/Z_shell) shell.~~
This is probably related to multiple python environments.
The default python environment that ships with 10.15 is `2.7` and the user will try to install `3.6` or greater to run `meltano` but macOS is probably not handling properly aliasing and version usage.
issue