Python 2.4 or higher is required

[skip ci]
Merge branch '1.5' into 1.6

[skip ci]
Python 2.5 or higher is required

[skip ci]
Merge branch '1.6' into 1.7

[skip ci]
Python 2.6 or 2.7 is required

[skip ci]
Merge branch '1.7' into 2.0

[skip ci]