Introduce a PythonFile object, and use it everywhere.

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

lldb/unittests/ScriptInterpreter/Python/PythonDataObjectsTests.cpp

@@ -9,6 +9,8 @@
 
 #include "gtest/gtest.h"
 
+#include "lldb/Host/File.h"
+#include "lldb/Host/FileSystem.h"
 #include "lldb/Host/HostInfo.h"
 #include "Plugins/ScriptInterpreter/Python/lldb-python.h"
 #include "Plugins/ScriptInterpreter/Python/PythonDataObjects.h"
@@ -373,3 +375,10 @@ TEST_F(PythonDataObjectsTest, TestPythonDictionaryToStructuredDictionary)
     EXPECT_STREQ(string_value0, string_sp->GetValue().c_str());
     EXPECT_EQ(int_value1, int_sp->GetValue());
 }
+
+TEST_F(PythonDataObjectsTest, TestPythonFile)
+{
+    File file(FileSystem::DEV_NULL, File::eOpenOptionRead);
+    PythonFile py_file(file, "r");
+    EXPECT_TRUE(PythonFile::Check(py_file.get()));
+}