Always use binary mode in NamedTempoeraryFile

Text mode would enable auto line ending translation, but we want to handle
them ourselves (in io.open) instead. This would not affect the ability to
write text files (io.open does the right thing as long as we give it the
correct mode).

pipenv/_compat.py

@@ -9,7 +9,7 @@ import io
 import os
 import six
 import warnings
-from tempfile import _bin_openflags, gettempdir, _mkstemp_inner, mkdtemp, _text_openflags
+from tempfile import _bin_openflags, gettempdir, _mkstemp_inner, mkdtemp
 from .utils import (logging, rmtree)
 
 try:
@@ -258,13 +258,12 @@ def NamedTemporaryFile(
     if os.name == "nt" and delete:
         flags |= os.O_TEMPORARY
     if six.PY2:
-        flags = _text_openflags if 'b' not in mode else flags
         (fd, name) = _mkstemp_inner(dir, prefix, suffix, flags)
     else:
         (fd, name) = _mkstemp_inner(dir, prefix, suffix, flags, output_type)
     try:
         file = io.open(
-            fd, mode, buffering=buffering, newline=newline, encoding=encoding
+            fd, mode, buffering=buffering, newline=newline, encoding=encoding,
         )
         return _TemporaryFileWrapper(file, name, delete)