Fix T67266: .obj import error with mtllib name in quotes - regression from 2.79b.

While this is not officialy part of OBJ format, some softwares 'solve'
the spaces-in-filenames issue by delimiting those with quotes.

Since this is not too much a hassle, let's add back support for this.

Based on work from Robert Guetzkow (@rjg), thanks.

Note: not sure whether this should be ported to 2.80 release, while this
change should be reasonably safe, it's not an obvious one-liner either,
and the issue is not really critical (don’t think any major software
uses that trick?)...

io_scene_obj/__init__.py

@@ -21,7 +21,7 @@
 bl_info = {
     "name": "Wavefront OBJ format",
     "author": "Campbell Barton, Bastien Montagne",
-    "version": (3, 5, 9),
+    "version": (3, 5, 10),
     "blender": (2, 80, 0),
     "location": "File > Import-Export",
     "description": "Import-Export OBJ, Import OBJ mesh, UV's, materials and textures",

io_scene_obj/import_obj.py

@@ -62,7 +62,21 @@ def filenames_group_by_ext(line, ext):
     """
     Splits material libraries supporting spaces, so:
     b'foo bar.mtl baz spam.MTL' -> (b'foo bar.mtl', b'baz spam.MTL')
+    Also handle " chars (some softwares use those to protect filenames with spaces, see T67266... sic).
     """
+    # Note that we assume that if there are some " in that line,
+    # then all filenames are properly enclosed within those...
+    start = line.find(b'"') + 1
+    if start != 0:
+        while start != 0:
+            end = line.find(b'"', start)
+            if end != -1:
+                yield line[start:end]
+                start = line.find(b'"', end + 1) + 1
+            else:
+                break
+        return
+
     line_lower = line.lower()
     i_prev = 0
     while i_prev != -1 and i_prev < len(line):
@@ -79,8 +93,16 @@ def obj_image_load(context_imagepath_map, line, DIR, recursive, relpath):
     But we try all space-separated items from current line when file is not found with last one
     (users keep generating/using image files with spaces in a format that does not support them, sigh...)
     Also tries to replace '_' with ' ' for Max's exporter replaces spaces with underscores.
+    Also handle " chars (some softwares use those to protect filenames with spaces, see T67266... sic).
     """
     filepath_parts = line.split(b' ')
+
+    start = line.find(b'"') + 1
+    if start != 0:
+        end = line.find(b'"', start)
+        if end != 0:
+            filepath_parts = (line[start:end],)
+
     image = None
     for i in range(-1, -len(filepath_parts), -1):
         imagepath = os.fsdecode(b" ".join(filepath_parts[i:]))