write_po() with width=None breaks header comment

[benhoyt]

pofile.write_po() with width=None doesn't output a line feed after the header comment. And read_po() strips the last line feed on the header comment -- which is fine, but the two together mean that if you read_po() and then write_po() with width=None it has the effect of commenting out the initial msgid "".

Complete example:

import StringIO
import babel.messages.pofile as pofile
fin = StringIO.StringIO('# header comment\nmsgid ""\nmsgstr ""\n')
catalog = pofile.read_po(fin)
fout = StringIO.StringIO()
pofile.write_po(fout, catalog, width=None)
print fout.getvalue()

This prints out:

# header commentmsgid ""
msgstr ""
"Project-Id-Version: PROJECT VERSION\n"
...

As you can see, msgid is put on the last header comment line.

To fix, simply replace these two lines in pofile.py:

                comment_header = u'\n'.join(lines) + u'\n'
            _write(comment_header)

with:

                comment_header = u'\n'.join(lines)
            _write(comment_header + u'\n')