Add error message with Rigaku validation failure

Author: briantoby

GSASII/imports/G2pwd_rigaku.py

@@ -167,7 +167,8 @@ def ContentsValidator(self, filename):
                 self.powderentry[0] = filename
                 self.comments = []
                 return True
-            except:
+            except Exception as msg:
+                self.errors = f'rasx open/read error\n{msg}'
                 return False
         else:
             fp.seek(0)