Remove use of exec

[djperrefort]

Codacy detected an issue:

Message: Use of exec detected.

Currently on:

• Commit: c5be901
• File: setup.py
• LineNum: 24

[15garzab]

Seems like it's just being used to read the version number from version.py into the dictionary version_ns. A simple key-value entry would suffice in line 24:
version_ns[__version__] = 1.2.3.
The last part will obviously not be hard-coded.