Recognised line endings differs for pofile(source) vs. pofile(path)

[eemeli]

This code is a bit buggy:

https://github.com/izimobil/polib/blob/bcb2bbab34448ca2e703a364ee523a6241eeff72/polib.py#L1268-L1275

When the pofile argument is a path, the file is opened in text mode, which means that iterating it will result in lines split by universal newlines. When the argument is a source string, it's split into lines with splitlines(), which recognises a wider collection of line endings.

The former is the right thing to do, while the latter will cause errors with messages that contain some of the additional characters.