It snuck past the pep8 tool, but not past you :wink:
I've three alternatives:
```
            use_symbol = (not units.is_time() and
                          not units.is_time_reference() and
                          len(units.symbol) < len(str(units)))
            if use_symbol:
                units = units.symbol
```
or
```
            if (
                not units.is_time() and not units.is_time_reference() and
                len(units.symbol) < len(str(units))
            ):
                units = units.symbol
```
or
```
            if not units.is_time() and not units.is_time_reference() and \
               len(units.symbol) < len(str(units)):
                units = units.symbol
```
Which one do you fancy?