build error: tlmgr not found

# Steps to reproduce:

1. clone repo
2. `cd` into it
3. `sudo docker build -t latex .`

# expected result

Build completes without error

# actual result

```
Step 9/10 : RUN tlmgr install latexmk
 ---> Running in cfb0b64790c9
/bin/sh: 1: tlmgr: not found
The command '/bin/sh -c tlmgr install latexmk' returned a non-zero code: 127
```