Work around pypy testing issue

A recent release of setuptools appears to have introduced a bug that
causes the pypy gate tests to fail. This applies a temporary workaround
that should restore pypy testing while the root cause of the problem is
researched.

The work around is suggested in the comment in bug 1290562.

Change-Id: Iac2ec604447b1638550219cd2e407daf188f8ede
Partial-Bug: 1290562

tox.ini

@@ -14,6 +14,11 @@ deps = -r{toxinidir}/requirements.txt
        -r{toxinidir}/test-requirements.txt
 commands = python setup.py testr --testr-args='{posargs}'
 
+[testenv:pypy]
+deps = setuptools<3.2
+       -r{toxinidir}/requirements.txt
+       -r{toxinidir}/test-requirements.txt
+
 [testenv:pep8]
 commands = flake8
 distribute = false