Making sure we're ready for python3

Stops making use of the builtin cmp function, and replaces
it with the recommended (a > b) - (a < b).

Switches pep8 python to python3

Change-Id: If4a45108fe93080f9967e2ac26d681b8dd5c7fc2

oslogmerger/oslogmerger.py

@@ -110,7 +110,8 @@ class LogEntry(object):
         self.data += EXTRALINES_PADDING + line
 
     def __cmp__(self, other):
-        return cmp(self.dt, other.dt) * 2 + cmp(self.alias, other.alias)
+        return (self._cmp(self.dt, other.dt) * 2 +
+                self._cmp(self.alias, other.alias))
 
     def __lt__(self, other):
         return self.dt < other.dt or (self.dt == other.dt and
@@ -119,6 +120,10 @@ class LogEntry(object):
     def __str__(self):
         return '%s [%s] %s' % (self.dt_str, self.alias, self.data.rstrip('\n'))
 
+    @staticmethod
+    def _cmp(a, b):
+        return (a > b) - (a < b)
+
 
 class LogParser(object):
     def __init__(self, filename, cfg):

tox.ini

@@ -1,5 +1,5 @@
 [tox]
-envlist = py35,py36,py27,pep8
+envlist = py35,py36,py37,py27,pep8
 minversion = 2.3.2
 skipsdist = True
 
@@ -24,7 +24,7 @@ setenv = OS_TEST_TIMEOUT={env:OS_TEST_TIMEOUT:180}
 commands = false
 
 [testenv:pep8]
-basepython = python2.7
+basepython = python3
 deps =
   {[testenv]deps}
 commands=