shape issue in load_workbook

Created originally on Bitbucket by JeremKoneo (Jeremie Magnette)

Hello, as asked in #971, I'm creating a new issue for my problem.

I encounter an exception when loading one of my excel files (very simple example attached). It seems to be ML_Drawing related. I'm using openpyxl 2.5.8. If I remove the shapes/arrows, then the issue disappear.

I've seen that this issue comes a lot here (mainly because ML_Drawing API is not open ?). Do you think that it would be feasible to not crash but better add a "warning/error" mechanism, that could be enabled, allowing users to still read problematic files ? This system would still allow users to give you feedback on what is missing, while still being capable to use the 2.5.x openpyxl version.

Right now, because I cannot delete those shapes (Client's file), I will downgrade to 2.4.x version of openpyxl.

Attachments: shape_error.xlsx