Hm, no benefit in leaving this as a generator and the NotImplementedError seems very unnecessary:

def _finalize(self, commands, ext):
    script = self.command_join.join((*commands, "))  # add terminating newline

    if ext:
        # the default mode is 'w+b', and universal new lines don't work in that mode
        # command_join should account for that
        with Utf8NamedTemporaryFile('w+', suffix=ext, delete=False) as tf:
            tf.write(script)
        return tf.name
    else:
        return script

Where's the NotImplementedError

line 135 of conda/activate.py

I guess ext could be the empty string sometimes? However it's not related to concatv in any way

I would rather leave it as chain() because I'm not familiar with arg unpacking.

@kenodegard do you need this PR to use *arg unpacking whenever it is possible?

Yeah, agreed that NotImplementedError isn't useful here, it's kind of misused for this case, since that's supposed to be an exception for base classes that require certain methods to be overridden in subclasses.

We need the indirect module from conda.tlz import x to place these two lines in one place (the indirection module), instead of everywhere that particular toolz is uzed

Let's add this to conda.common as well.