[LyX/master] ePub: improve compatibility with Python 2.

[Thibaut Cuvelier]

commit b1febf112ddb7dd99aeef90d5285cba34ff92edc
Author: Thibaut Cuvelier <tcuvelier at lyx.org>
Date:   Mon Feb 8 02:36:28 2021 +0100

    ePub: improve compatibility with Python 2.
---
 lib/scripts/docbook2epub.py |    1 +
 1 files changed, 1 insertions(+), 0 deletions(-)

diff --git a/lib/scripts/docbook2epub.py b/lib/scripts/docbook2epub.py
index 1d39962..94375a9 100644
--- a/lib/scripts/docbook2epub.py
+++ b/lib/scripts/docbook2epub.py
@@ -19,6 +19,7 @@ import shutil
 import sys
 import tempfile
 import zipfile
+from io import open  # Required for Python 2.
 
 
 def _parse_nullable_argument(arg):