Use Python 3.x by default for testing

This requires updating newer hacking which requires
some small fixes for pep8 to pass. Also adjust sphinx
dependencies so that py2.7 environment continues to work.

Change-Id: I576a6c42867a3fed7cc7090bd4a6219de3bced66

bindep/depends.py

@@ -658,8 +658,8 @@ def _cmp_segment(l_str, r_str):
     while (r_offset < len(r_str)) or (l_offset < len(l_str)):
         r_char = r_str[r_offset:r_offset + 1]
         l_char = l_str[l_offset:l_offset + 1]
-        if ((not r_char or r_char.isdigit())
-            and (not l_char or l_char.isdigit())):
+        if ((not r_char or r_char.isdigit()) and
+            (not l_char or l_char.isdigit())):
             l_int, l_offset = _find_int(l_str, l_offset)
             r_int, r_offset = _find_int(r_str, r_offset)
             diff = l_int - r_int

test-requirements.txt

@@ -1,4 +1,4 @@
-hacking>=0.10.0,<0.11
+hacking
 
 coverage>=3.6
 fixtures>=0.3.12
@@ -6,6 +6,7 @@ mock>=2.0  # BSD
 python-subunit
 testrepository>=0.0.13
 testtools>=0.9.27
-sphinx>1.6.1  # BSD
+sphinx!=1.6.6,!=1.6.7,<2.0.0;python_version=='2.7'  # BSD
+sphinx!=1.6.6,!=1.6.7,!=2.1.0;python_version>='3.4'  # BSD
 openstackdocstheme>=1.24.1  # Apache-2.0
 sphinxcontrib-programoutput  # BSD license

tox.ini

@@ -1,9 +1,11 @@
 [tox]
 envlist = py35,py27,pypy,pep8
 skipdist = True
+ignore_basepython_conflict=true
 
 [testenv]
 usedevelop = True
+basepython = python3
 install_command = pip install -U {opts} {packages}
 setenv = VIRTUAL_ENV={envdir}
 deps = -r{toxinidir}/test-requirements.txt