Invoke: inv command not found in ubuntu (in docker)

[kenden]

Description

After installing pyinvoke in ubuntu following the docs at .
http://www.pyinvoke.org/installing.html#basic-installation

when I try running inv, I get command not found

Note: invoke 1.x and 1.2 work fine on macOS, installed with brew.

Steps to reproduce

# start ubuntu in a container:
$ docker run -it --rm ubuntu:18.10
# In container now
$ apt update && apt install -y python3 python3-pip

$ pip3 install pyinvoke
(...)
Successfully installed pyinvoke-1.0.4
# Now pyinvoke is installed

$ inv
bash: inv: command not found
$ invoke
bash: invoke: command not found
$ pyinvoke
bash: pyinvoke: command not found
$ echo $PATH
/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin

Same results with ubuntu:16.04 and ubuntu:18.04, with the same results.
Both also install pyinvoke-1.0.

Expected

Typing inv or invoke shows its available subcommands.

[kenden]

I installed the wrong package, it's not
pip3 install pyinvoke
but
pip3 install invoke
Argh. Closing. I hope this ticket can help someone.