Show a warning/message when loading Org modules requiring external packages (was: :session for Julia in org babel?)

[Ihor Radchenko]

"Christopher M. Miles" <numbchild@gmail.com> writes:

> What about write a elisp function to automatic the installation of those
> required two Julia packages? If not, at least raise a warning for user
> to install those two packages after detection not exist. WDYT?

Installation is not a good idea because there are multiple alternative
package managers in Emacs. Some of them explicitly require user to add
code into init.el (I am referring to straight.el).

However, we may, indeed, show some helpful warning/message.

A reasonable place to implement such message is org-load-modules-maybe.
It might catch the relevant errors and show the message.

Patches are welcome!

-- 
Ihor Radchenko,
Org mode contributor,
Learn more about Org mode at https://orgmode.org/.
Support Org development at https://liberapay.com/org-mode,
or support my work at https://liberapay.com/yantar92