tox failed: No package 'libvirt' found

Downloading/unpacking jinja2 (from -r /home/nobuto/dev/maas-deployer_fix-sticky-ip/requirements.txt (line 3))
Downloading/unpacking libvirt-python (from -r /home/nobuto/dev/maas-deployer_fix-sticky-ip/requirements.txt (line 4))
  Running setup.py (path:/tmp/pip-build-d8iwGw/libvirt-python/setup.py) egg_info for package libvirt-python
    Package libvirt was not found in the pkg-config search path.
    Perhaps you should add the directory containing `libvirt.pc'
    to the PKG_CONFIG_PATH environment variable
    No package 'libvirt' found
    Package libvirt was not found in the pkg-config search path.
    Perhaps you should add the directory containing `libvirt.pc'
    to the PKG_CONFIG_PATH environment variable
    No package 'libvirt' found

    file build/libvirt.py (for module libvirt) not found
    file build/libvirt_qemu.py (for module libvirt_qemu) not found
Downloading/unpacking lxml (from -r /home/nobuto/dev/maas-deployer_fix-sticky-ip/requirements.txt (line 5))
  Running setup.py (path:/tmp/pip-build-d8iwGw/lxml/setup.py) egg_info for package lxml
    /usr/lib/python2.7/distutils/dist.py:267: UserWarning: Unknown distribution option: 'bugtrack_url'
      warnings.warn(msg)
    Building lxml version 3.4.4.
    Building without Cython.
    Using build configuration of libxslt 1.1.28

    warning: no previously-included files found matching '*.py'

I was missing libvirt-dev, python-dev, libxslt1-dev and zlib1g-dev package.

ok, missing packages from trusty ubuntu-cloud image as follows.

$ sudo apt-get install python-tox pkg-config libvirt-dev python-dev libxslt1-dev zlib1g-dev
$ tox
 -> works.