also check journalctl for releated vshd.elf errors.

Seems to work as expected on tip of tree.

Running "x-terminal-emulator" produces a new terminal window.

Running "x-terminal-emulator <some command>" creates a new terminal window
that executes that command and then closes. This is somewhat unhelpful if the
command fails, but still normal behavior for a terminal emulator.

Note that "python" isn't available by default in the container, you should use "python3" instead. Because of this "x-terminal-emulator python" will cause
a terminal window to briefly appear before closing instead of the expected
python command prompt.

Feel free to re-open this with more information if you think the above is incorrect.

pyton was just an example, the problem is when <some command> isn't just a word:

try:
x-terminal-emulator xterm
should work

then
x-terminal-emulator /usr/bin/xterm
doesn't work

then check logs:
sudo journalctl -b -t vshd.elf -e

I can confirm this doesn't work on 11242.0.0.  You end up with an error in journalctl of the nature:

vshd.elf: Failed to exec '???????????term': No such file or directory

And the bad chars in it change each time you exec it.

It looks like this is an issue in the character escaping that occurs between the original command and being received by the crostini terminal.

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/f02661f81d53c8b3f24a455839dfcf1c356b271a

commit f02661f81d53c8b3f24a455839dfcf1c356b271a
Author: Nicholas Verne <nverne@chromium.org>
Date: Tue Nov 20 00:57:42 2018

Fix up terminal args passed to crosh in its args array.

When Crostini users invoke x-terminal-emulator $CMD, the contents of CMD
are eventually passed by CrostiniManager in an args[] array to crosh as part
of its URL.

Fixed in this CL: incorrect usage of vector<StringPiece>.
We were adding more pieces in line 1065 which were derived from temporaries
(return values of net::Escape...). The temporaries were thrown away but the
pieces still pointed to the same memory and we sent nonsense to
base::JoinString().

Bug:  898111 
Change-Id: If5d3ffcb6ab28d01698ee48cd7fd3d2230381f95
Reviewed-on: https://chromium-review.googlesource.com/c/1341282
Commit-Queue: Nicholas Verne <nverne@chromium.org>
Reviewed-by: Mike Frysinger <vapier@chromium.org>
Reviewed-by: Ben Wells <benwells@chromium.org>
Cr-Commit-Position: refs/heads/master@{#609539}
[modify] https://crrev.com/f02661f81d53c8b3f24a455839dfcf1c356b271a/chrome/browser/chromeos/crostini/crostini_manager.cc