DepErrors checks there are any errors resolving dependencies for `pkgpath`.

DirExists tests whether `filename` exists and is a directory.

FileExists tests whether the file at `filename` exists and is not a directory.

Getenv retrieves the value of the environment variable named by the key.

GetModDir gets the absolute directory of the module containing the package with path `pkgpath`.

GetPkgDir gets the absolute directory containing the package with path `pkgpath`.