cdnjs-index: force encoding on writing files
cdnjs-index: force encoding on writing files

Some strange bug interaction between our gridengine environment
and old versions from the world of python 3 cause an encoding error
without specifying it when writing the files out.

Bug: T196668
Change-Id: I77c9b8fa6273339438a799420449e82e5397a7c6

wikimedia/labs-tools-cdnjs-index