cannot install libsnmp-dev in stretch, wondering about reasonable next steps

[Dan Hitt <dan.hitt@gmail.com>]

I'm trying to install libsnmp-dev in stretch (debian 9) using the command
   sudo apt-get install libsnmp-dev

This results in an error:
----------
Some packages could not be installed. This may mean that you have
requested an impossible situation or if you are using the unstable
distribution that some required packages have not yet been created
or been moved out of Incoming.
The following information may help to resolve the situation:

The following packages have unmet dependencies:
 udev : Breaks: systemd (< 232-20) but 232-14 is to be installed
E: Error, pkgProblemResolver::Resolve generated breaks, this may be
caused by held packages.
----------

First, i'm not even sure of the interpretation of the error.  Does it
mean my systemd version is too large?  Does it mean my systemd version
is too small?  Note that 'systemd --version' returns 232 on my system,
without any extra info that i can see, so it's hard for me to even do
some sanity checking.

So i would like to understand what the error means, and then, what
would be a reasonable course of action to take.  (E.g., updating
systemd?  Compiling libsnmp-dev by hand and installing in /usr/local?
Filing a bug report somewhere?)

Thanks in advance for any clues.

dan