seleniumserver: stop-on-error plone.recipe.command

If this command fail, instanciation should not succeed.

software/seleniumserver/buildout.hash.cfg

@@ -19,4 +19,4 @@ md5sum = c4ac5de141ae6a64848309af03e51d88
 
 [template-selenium]
 filename = instance-selenium.cfg.in
-md5sum = 4f557a7b3aa9b4df1ca1fa6a754ca657
+md5sum = 04da37bb328b1e50766bb47fa9e3172c

software/seleniumserver/instance-selenium.cfg.in

@@ -186,6 +186,7 @@ extra-args=-t ecdsa -b 521
 
 [ssh-key-fingerprint-command]
 recipe = plone.recipe.command
+stop-on-error = true
 # recent openssh client display ECDSA key's fingerprint as SHA256
 command = ${openssh-output:keygen} -lf $${ssh-host-ecdsa-key:output}