'Set environment variable ``name`` to ``value``.  If ``prepend``
is a character, read the current environment variable value
and prepend the ``value`` adjoined with the ``prepend`` character.'

def setenv(self, name, value, prepend=None):

    value = str(value)
    if (prepend and (name in os.environ)):
        value = ((value + prepend) + os.environ[name])
    self.setitem(os.environ, name, value)
