indentAfterAllSeps = (str, sep, indents) => {
  const [firstLine, ...restLines] = stringSplit(str, sep);
  const indentedRest = arrayFlatMap(restLines, line => [sep, ...indents, line]);
  return ['', firstLine, ...indentedRest];
}
Implement the `VirtualConsole` API badly by turning all calls into
calls on `tlogger`. We need to do this to have `console` logging
turn into calls to Ava's `t.log`, so these console log messages
are output in the right place.

@param {Logger} tlogger
@returns {VirtualConsole}