kicad: set output file in constant

kicad_lib.rb

@@ -16,6 +16,7 @@ credentials = {}
 JSON.parse(IO.read(CREDENTIALS)).each {|key,value| credentials[key.to_sym] = value}
 Mysql2::Client.default_query_options.merge!(:as => :hash)
 db = Mysql2::Client.new(credentials)
+KICAD_FILE = "partdb.kicad_dbl"
 
 puts "create part to model views"
 
@@ -66,6 +67,7 @@ categories.each do |category|
   kicad_dbl["libraries"] << library
 end
 
-File.open("partdb.kicad_dbl", "w") do |file|
+puts "writing KiCad database library file to #{KICAD_FILE}"
+File.open(KICAD_FILE, "w") do |file|
   file.write kicad_dbl.to_json
 end