The invisible enemy

$ hpost - "Fly Away Home"
: No such file or directory

Huh.

$ head -n 1 bin/hpost
#!/usr/bin/env python3
$ type python3
python3 is /usr/local/bin/python3
$ /usr/bin/env python3
Python 3.6.6 (default, Jul 27 2018, 04:04:20)
...
$

???

…

When copying scripts from Windows, it helps to de-CRLF them. env was looking for python3^M, and unsurprisingly, didn’t find it.