Hugo: Install Python on Linux: 2 more dependencies

hugo/content/installation/py/linux.md

@@ -21,14 +21,15 @@ Python version manager [pyenv](https://github.com/pyenv/pyenv).
 To provide a backend for the Python plotting module matplotlib,
 install the GUI toolkit Tk before installing pyenv (otherwise,
 you will need to rerun `pyenv install <version>`).
+Also, two other development packages are required.
+A warning about missing sqlite3 support can be ignored.
 
-| Distribution | Package  |
-| ------------ | -------  |
-| Debian       | tk-dev   |
-| Redhat       | tk-devel |
-| Archlinux    | Tk       |
+| Distribution | Packages  |
+| ------------ | --------  |
+| Debian       | tk-dev   libssl-dev   libreadline-dev |
+| Redhat       | tk-devel libssl-devel libreadline-devel |
+| Archlinux    | Tk       ? ? |
 
-A warning about missing sqlite3 support can be ignored.
 
 #### Python in pyenv