Avoid opening files with deprecated 'U' mode (#269)
Opening files with 'U' mode is deprecated. When running tests with
Python warnings enabled, the warnings of the following form are emitted:
DeprecationWarning: 'U' mode is deprecated
return open(name, 'rU')
To open files with universal newlines on both Ptyhon 2 & 3, use the io
module. It defaults to opening with universal newlines and doesn't emit
a warning.
https://docs.python.org/3/library/io.html
> When reading input from the stream, if newline is None, universal
> newlines mode is enabled.2 files changed
