Fix #4783: Sphinx crashed when drives of srcdir and outdir are different

1 files changed, 8 insertions, 1 deletions

diff --git a/sphinx/util/osutil.py b/sphinx/util/osutil.py
index af87caf9a..fdcbda9a6 100644
--- a/sphinx/util/osutil.py
+++ b/sphinx/util/osutil.py
@@ -205,14 +205,21 @@ def ustrftime(format, *args):
             return r.encode().decode('unicode-escape')
 
 
-def safe_relpath(path, start=None):
+def relpath(path, start=os.curdir):
     # type: (unicode, unicode) -> unicode
+    """Return a relative filepath to *path* either from the current directory or
+    from an optional *start* directory.
+
+    This is an alternative of ``os.path.relpath()``.  This returns original path
+    if *path* and *start* are on different drives (for Windows platform).
+    """
     try:
         return os.path.relpath(path, start)
     except ValueError:
         return path
 
 
+safe_relpath = relpath  # for compatibility
 fs_encoding = sys.getfilesystemencoding() or sys.getdefaultencoding()  # type: unicode