Stderr.writefln

[%u]

I used to use

    import std.stream;

and

    stderr.writefln( ... );

to log errors. I recently upgraded to v0.175 (from v0.12x), and this now generates reams of errors:

    realtest.d(13): Error: undefined identifier stderr
    realtest.d(13): Error: undefined identifier stderr
    realtest.d(13): Error: no property 'writefln' for type 'int'
    realtest.d(13): Error: function expected before (), not 1 of type int

I've found that importing std.stdio will give me back stderr, but the second two errors persist.
I've tried searching this site for references, but nothing explains the change, or how to retrieve the old functionality?

Thanks, N.