Terser logging

The development logging is currently a bit overwhelming. This PR trims it down a bit, à la 39046680a.
While we are at this, maybe we could try to catch and explain a few of the common ES-related exceptions that new developers might meet.

For example, when the ICU modules for ES is not installed (which, by the way, is not even mentioned in any of our install documents), we get a bunch of long strack traces, instead of a clear explanation of what the problem is, with suggestions about how to solve it.