Hello,
I take it that you have made changes to the Mibew source and you are trying to build a new package, right?
I'm not sure how gulp works, but you may get some clues in the build script gulpfile.js. It seems as if you are having trouble with the task bower-install, located at
https://github.com/Mibew/mibew/blob/master/src/gulpfile.js#L120. It also looks like line 154 of the build script is where the error is occurring - not sure if it is coincidence or just how bower reports its errors since it is pointing to events.js:154.
The error seems to be a write issue. Do you have write permissions to the directory where it is trying to install bower?
Another thing, you can search "Error: write EPIPE" in the gulp forums to find out what the possible causes are.
Hope this points you in the right direction to solve your problem.