I do still see the issue on Python 3.7b3:

$ python ~/Dropbox/bin/scripts/which-line-ending onefile.py
Line ending is '\n'
$ python ~/Dropbox/bin/scripts/which-line-ending otherfile.py
Line ending is '\r\n'
$ python -V
Python 3.7.0b3
$ python -m lib2to3 . -w
RefactoringTool: Skipping optional fixer: buffer
RefactoringTool: Skipping optional fixer: idioms
RefactoringTool: Skipping optional fixer: set_literal
RefactoringTool: Skipping optional fixer: ws_comma
RefactoringTool: Refactored ./onefile.py
--- ./onefile.py        (original)
+++ ./onefile.py        (refactored)
@@ -1 +1 @@
-print 'hello world'
+print('hello world')
RefactoringTool: Refactored ./otherfile.py
--- ./otherfile.py      (original)
+++ ./otherfile.py      (refactored)
@@ -1 +1 @@
-print 'hello world'
+print('hello world')
RefactoringTool: Files that were modified:
RefactoringTool: ./onefile.py
RefactoringTool: ./otherfile.py
$ $ python ~/Dropbox/bin/scripts/which-line-ending onefile.py
Line ending is '\n'
$ python ~/Dropbox/bin/scripts/which-line-ending otherfile.py
Line ending is '\n'