[3.6] bpo-12382: Make OpenDatabase() raise better exception messages (GH-4528)

[miss-islington]

Previously, 'msilib.OpenDatabase()' function raised a
cryptical exception message when it couldn't open or
create an MSI file. For example:

Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
_msi.MSIError: unknown error 6e

(cherry picked from commit 4864a61)

https://bugs.python.org/issue12382

[miss-islington]

@berkerpeksag: Backport status check is done, and it's a success ✅ .

[miss-islington]

Thanks, @berkerpeksag!