Set coverage to specific version as 4+ is not Python 3.2 compatible

Author: MRigal

setup.py

@@ -52,12 +52,13 @@ def get_version(version_tuple):
 extra_opts = {"packages": find_packages(exclude=["tests", "tests.*"])}
 if sys.version_info[0] == 3:
     extra_opts['use_2to3'] = True
-    extra_opts['tests_require'] = ['nose', 'coverage', 'blinker', 'Pillow>=2.0.0']
+    extra_opts['tests_require'] = ['nose', 'coverage==3.7.1', 'blinker', 'Pillow>=2.0.0']
     if "test" in sys.argv or "nosetests" in sys.argv:
         extra_opts['packages'] = find_packages()
         extra_opts['package_data'] = {"tests": ["fields/mongoengine.png", "fields/mongodb_leaf.png"]}
 else:
-    extra_opts['tests_require'] = ['nose', 'coverage', 'blinker', 'Pillow>=2.0.0', 'python-dateutil']
+    # coverage 4 does not support Python 3.2 anymore
+    extra_opts['tests_require'] = ['nose', 'coverage==3.7.1', 'blinker', 'Pillow>=2.0.0', 'python-dateutil']
 
     if sys.version_info[0] == 2 and sys.version_info[1] == 6:
         extra_opts['tests_require'].append('unittest2')