fatal exit if assure_exists is failed

bin/epm-assure

@@ -39,7 +39,7 @@ __epm_assure()
             info "Command $1 is exists: $compath"
             epm qf "$compath"
         fi
-        return
+        return 0
     fi
 
     # TODO: use package name normalization

bin/epm-sh-functions

@@ -297,7 +297,7 @@ assure_exists()
 	load_helper epm-assure
 	local package="$2"
 	[ -n "$package" ] || package="$(__get_package_for_command "$1")"
-	__epm_assure "$1" $package
+	__epm_assure "$1" $package || fatal "Can't assure in '$1' command"
 }
 
 # TODO: improve and drop!