Add python3.7 support (prometheus#418)

Signed-off-by: Stanislav Kudriashev <stas.kudriashev@gmail.com>

Author: skudriashev

.travis.yml

@@ -19,8 +19,14 @@ matrix:
       env: TOXENV=py35
     - python: "3.6"
       env: TOXENV=py36
-    - python: "3.6"
-      env: TOXENV=py36-nooptionals
+    - python: "3.7"
+      env: TOXENV=py37
+      dist: xenial
+      sudo: true
+    - python: "3.7"
+      env: TOXENV=py37-nooptionals
+      dist: xenial
+      sudo: true
     - python: "pypy"
       env: TOXENV=pypy
     - python: "pypy3"

setup.py

@@ -35,6 +35,7 @@
         "Programming Language :: Python :: 3.4",
         "Programming Language :: Python :: 3.5",
         "Programming Language :: Python :: 3.6",
+        "Programming Language :: Python :: 3.7",
         "Programming Language :: Python :: Implementation :: CPython",
         "Programming Language :: Python :: Implementation :: PyPy",
         "Topic :: System :: Monitoring",

tests/test_gc_collector.py

@@ -1,8 +1,8 @@
 from __future__ import unicode_literals
 
 import gc
-import sys
 import platform
+import sys
 
 if sys.version_info < (2, 7):
     # We need the skip decorators from unittest2 on Python 2.6.

tox.ini

@@ -1,5 +1,5 @@
 [tox]
-envlist = coverage-clean,py26,py27,py34,py35,py36,pypy,pypy3,{py27,py36}-nooptionals,coverage-report,flake8
+envlist = coverage-clean,py26,py27,py34,py35,py36,py37,pypy,pypy3,{py27,py37}-nooptionals,coverage-report,flake8
 
 
 [base]
@@ -32,19 +32,16 @@ deps =
     {py27,py34,py35,py36,pypy,pypy3}: twisted
 commands = coverage run --parallel -m pytest {posargs}
 
-
 ; Ensure test suite passes if no optional dependencies are present.
 [testenv:py27-nooptionals]
 deps = 
     {[base]deps}
     futures
 commands = coverage run --parallel -m pytest {posargs}
 
-[testenv:py36-nooptionals]
-deps = {[base]deps}
+[testenv:py37-nooptionals]
 commands = coverage run --parallel -m pytest {posargs}
 
-
 [testenv:coverage-clean]
 deps = coverage
 skip_install = true