Running pybitcointools & python-bitcoinlib concurrently
Not sure if you can do it as they seem to be the same package.
For python-bitcoinlib here:

Author: Vitalik Buterin
Home Page: http://github.com/vbuterin/pybitcointools
Package Index Owner: vbuterin
DOAP record: bitcoin-1.1.26.xml

For pybitcointools here:

Author: Vitalik Buterin
Home Page: http://github.com/vbuterin/pybitcointools
Package Index Owner: vbuterin
DOAP record: pybitcointools-1.1.15.xml

They point to the same package on github (just different versions) and running them at the same time is probably not a good idea. My guess is that Vitalik changed the python package name from pybitcointools to bitcoin when he realized the second was available.
That said, if you really need to use both packages, you can do something like this answer. Note you'll have to install manually, probably installing from source using github.