Python file handling got an overhaul in Python 3, and it affects
the way we have to interact with files. Notably:
1) `PyFile_FromFile` no longer exists, and instead we have to use
`PyFile_FromFd`. This means having a way to get an fd from
a FILE*. For this we reuse the lldb_private::File class to
convert between FILE*s and fds, since there are some subtleties
regarding ownership rules when FILE*s and fds refer to the same
file.
2) PyFile is no longer a builtin type, so there is no such thing as
`PyFile_Check`. Instead, files in Python 3 are just instances
of `io.IOBase`. So the logic for checking if something is a file
in Python 3 is to check if it is a subclass of that module.
Additionally, some unit tests are added to verify that `PythonFile`
works as expected on Python 2 and Python 3, and
`ScriptInterpreterPython` is updated to use `PythonFile` instead of
manual calls to the various `PyFile_XXX` methods.
llvm-svn: 250444
9c40264fda