add check for reading ascii fbx files, was common annoyance that users are...

add check for reading ascii fbx files, was common annoyance that users are unaware that they try to import ascii files.

io_scene_fbx/import_fbx.py

@@ -828,6 +828,17 @@ def blen_read_light(fbx_tmpl, fbx_obj, global_scale):
     return lamp
 
 
+def is_ascii(filepath, size):
+    with open(filepath, 'r', encoding="utf-8") as f:
+        try:
+            f.read(size)
+            return True
+        except UnicodeDecodeError:
+            pass
+
+    return False
+
+
 def load(operator, context, filepath="",
          global_matrix=None,
          use_cycles=True,
@@ -843,6 +854,11 @@ def load(operator, context, filepath="",
     import os
     from . import parse_fbx
 
+    # detect ascii files
+    if is_ascii(filepath, 24):
+        operator.report({'ERROR'}, "ASCII FBX files are not supported %r" % filepath)
+        return {'CANCELLED'}
+
     try:
         elem_root, version = parse_fbx.parse(filepath)
     except: