backend name is now package manager name, error if incorrect in conf file

src/backends/baguette.cr

@@ -5,7 +5,7 @@ require "../backends.cr"
 
 class BaguetteBackend < Package::Backend::Packaging
 	def initialize
-		@name = "baguette"
+		@name = "package"
 	end
 
 	def package(context : Package::Context, package : Package::Package) : Bool

src/context.cr

@@ -283,7 +283,17 @@ class Package::Context
 				end
 			when "package-manager"
 				# Targeted package manager (default: package, for BaguetteOS).
+				begin
 					self.packaging_backend = value.as_s
+				rescue e
+					STDERR.puts "Error during selecting packaging backend: #{e}"
+					STDERR.puts "#{value.as_s} seems not to be a valid backend"
+					STDERR.puts "valid backends:"
+					@packaging_backends.each do |backend|
+						STDERR.puts "- #{backend.name}"
+					end
+					exit 1
+				end
 			end
 		end
 	end