Imports of package constraint

PathSynopsis
errorsPackage errors implements functions to manipulate errors.
strconvPackage strconv implements conversions to and from string representations of basic data types.
stringsPackage strings implements simple functions to manipulate UTF-8 encoded strings.
unicodePackage unicode provides data and functions to test some properties of Unicode code points.
unicode/utf8Package utf8 implements functions and constants to support text encoded in UTF-8.