Why does Wubi installation fail with "Error: 'None Type' object has no attribute 'get_info'"?
Solution 1:
Don't mount the image file, just put wubi.exe and the iso in same folder and then try, Don't mount it through any software
Solution 2:
Known bug, please re-download the ISO and verify MD5 hash
It appears this is a catch-all error usually thrown (shown) by Wubi not recognizing or reading some piece of data in the ISO used for installation, which in turn is caused by an error while downloading the ISO.
Please try separately downloading the 12.04 i386 desktop ISO, and verify that the MD5 hash matches. Then launch Wubi and point it to the downloaded ISO.