Hi users,
I have the following error installing Firedrake on ubuntu 16.04
(firedrake) hpc@hpc:~/firedrake/src/firedrake$ make alltest
    Building extension modules
Traceback (most recent call last):
  File "setup.py", line 8, in <module>
    import petsc4py
ImportError: No module named 'petsc4py'
    Linting firedrake codebase
    Linting firedrake test suite
    Linting firedrake scripts
    Running all regression tests
============================================ test session starts ============================================
platform linux -- Python 3.5.2, pytest-5.1.1, py-1.8.0, pluggy-0.12.0
rootdir: /home/hpc/firedrake/src/firedrake, inifile: setup.cfg
plugins: forked-1.0.2, xdist-1.29.0
collected 0 items / 1 errors                                                                                
================================================== ERRORS ===================================================
_______________________________________ ERROR collecting test session _______________________________________
../../lib/python3.5/site-packages/_pytest/config/__init__.py:436: in _importconftest
    return self._conftestpath2mod[conftestpath]
E   KeyError: local('/home/hpc/firedrake/src/firedrake/tests/extrusion/conftest.py')
During handling of the above exception, another exception occurred:
../../lib/python3.5/site-packages/_pytest/config/__init__.py:442: in _importconftest
    mod = conftestpath.pyimport()
../../lib/python3.5/site-packages/py/_path/local.py:701: in pyimport
    __import__(modname)
<frozen importlib._bootstrap>:969: in _find_and_load
    ???
<frozen importlib._bootstrap>:958: in _find_and_load_unlocked
    ???
<frozen importlib._bootstrap>:673: in _load_unlocked
    ???
../../lib/python3.5/site-packages/_pytest/assertion/rewrite.py:140: in exec_module
    exec(co, module.__dict__)
tests/extrusion/conftest.py:2: in <module>
    from firedrake import ExtrudedMesh, UnitSquareMesh, UnitIntervalMesh
firedrake/__init__.py:5: in <module>
    if "PETSC_DIR" in os.environ and not config["options"]["honour_petsc_dir"]:
E   TypeError: 'NoneType' object is not subscriptable
During handling of the above exception, another exception occurred:
../../lib/python3.5/site-packages/py/_path/common.py:377: in visit
    for x in Visitor(fil, rec, ignore, bf, sort).gen(self):
../../lib/python3.5/site-packages/py/_path/common.py:418: in gen
    dirs = self.optsort([p for p in entries
../../lib/python3.5/site-packages/py/_path/common.py:419: in <listcomp>
    if p.check(dir=1) and (rec is None or rec(p))])
../../lib/python3.5/site-packages/_pytest/main.py:606: in _recurse
    ihook = self.gethookproxy(dirpath)
../../lib/python3.5/site-packages/_pytest/main.py:424: in gethookproxy
    my_conftestmodules = pm._getconftestmodules(fspath)
../../lib/python3.5/site-packages/_pytest/config/__init__.py:420: in _getconftestmodules
    mod = self._importconftest(conftestpath.realpath())
../../lib/python3.5/site-packages/_pytest/config/__init__.py:450: in _importconftest
    raise ConftestImportFailure(conftestpath, sys.exc_info())
E   _pytest.config.ConftestImportFailure: (local('/home/hpc/firedrake/src/firedrake/tests/extrusion/conftest.py'), (<class 'TypeError'>, TypeError("'NoneType' object is not subscriptable",), <traceback object at 0x7f4728146088>))
!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! Interrupted: 1 errors during collection !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
============================================= 1 error in 0.29s ==============================================
Makefile:64: recipe for target 'test' failed
make: *** [test] Error 2