return instead of exit

install.sh

@@ -67,10 +67,7 @@ function sudo_root {
 ## MAIN
 
 set -Eeuo pipefail
-assert_supported_distro
-assert_bash
-sudo_root
-
+if assert_supported_distro && assert_bash && sudo_root; then
   if [[ ! -v MIAOU_BASH_DIR ]]; then
     MIAOU_BASH_DIR=/opt/miaou-bash
     export MIAOU_BASH_DIR
@@ -81,3 +78,6 @@ if once_installed; then upgrade; else install; fi
   if [[ $deployment_type_adjective == 'installed' ]]; then
     exec bash -l
   fi
+else
+  >&2 echo "MIAOU_BASH_ERROR: requirements failure"
+fi