return instead of exit

install.sh

@@ -67,17 +67,17 @@ function sudo_root {
 ## MAIN
 
 set -Eeuo pipefail
-assert_supported_distro
-assert_bash
-sudo_root
-
-if [[ ! -v MIAOU_BASH_DIR ]]; then
+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
-fi
+  fi
 
-deployment_type_adjective="${1:-installed}" # `miaou-bash --self-upgrade` provides the 'upgrade' term
-if once_installed; then upgrade; else install; fi
-if [[ $deployment_type_adjective == 'installed' ]]; then
+  deployment_type_adjective="${1:-installed}" # `miaou-bash --self-upgrade` provides the 'upgrade' term
+  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