Move test helpers like reload_2_3 and others to basedir

Also add __init__.py to allow relative imports

tests/utils_test.py

@@ -0,0 +1,57 @@
+import os
+import tempfile
+import shutil
+
+
+class patched_chdir(object):
+
+    """Just like chdir, but can be used in  `with` - sets back the old path at exit"""
+
+    def __init__(self, new_path):
+        self.old_path = os.getcwd()
+        self.new_path = new_path
+
+    def __enter__(self):
+        os.chdir(self.new_path)
+
+    def __exit__(self, type, value, traceback):
+        os.chdir(self.old_path)
+
+
+def create_temp_case(case_name, case_basedir=None, path_tmpdir=None):
+    case_basedir = case_basedir or __file__
+    with patched_chdir(os.path.dirname(case_basedir)):
+        path_test_cases = os.path.abspath("../testcases/")
+        path_case = os.path.join(path_test_cases, case_name)
+
+        path_tmpdir = path_tmpdir or tempfile.mkdtemp()
+        path_tmpdir_case = os.path.join(path_tmpdir, case_name)
+        shutil.copytree(path_case, path_tmpdir_case)
+
+    return path_tmpdir_case
+
+
+def reload_2_3(module_name):
+    '''
+    reload that works in all versions of Python.
+    Uses builtin reload in py2, imp.reload for <=py3.3,
+    importlib.reload for >=3.4
+
+    The module six has similar functionalities,
+    but would be too huge a dependency for this simple case.
+    '''
+
+    from sys import version_info
+    major_ver, minor_ver = version_info[:2]
+
+    if major_ver == 2:
+        reload(module_name)
+    elif major_ver == 3 and minor_ver <= 3:
+        import imp
+        imp.reload(module_name)
+    elif major_ver == 3 and minor_ver >= 4:
+        import importlib
+        importlib.reload(module_name)
+    else:
+        raise NotImplementedError("Not sure how to reload in "
+                                  "this version of Python, supported upto 3.x")