fix issue317: assertion rewriter support for the is_package method

CHANGELOG

@@ -11,6 +11,8 @@ Changes between 2.3.5 and 2.4.DEV
   for standard datatypes and recognise collections.abc.  Thanks to
   Brianna Laugher and Mathieu Agopian.
 
+- fix issue317: assertion rewriter support for the is_package method
+
 - fix issue335: document py.code.ExceptionInfo() object returned
   from pytest.raises(), thanks Mathieu Agopian.
 

_pytest/assertion/rewrite.py

@@ -150,12 +150,25 @@ class AssertionRewritingHook(object):
             mod.__file__ = co.co_filename
             # Normally, this attribute is 3.2+.
             mod.__cached__ = pyc
+            mod.__loader__ = self
             py.builtin.exec_(co, mod.__dict__)
         except:
             del sys.modules[name]
             raise
         return sys.modules[name]
 
+
+
+    def is_package(self, name):
+        try:
+            fd, fn, desc = imp.find_module(name)
+        except ImportError:
+            return False
+        if fd is not None:
+            fd.close()
+        tp = desc[2]
+        return tp == imp.PKG_DIRECTORY
+
 def _write_pyc(state, co, source_path, pyc):
     # Technically, we don't have to have the same pyc format as
     # (C)Python, since these "pycs" should never be seen by builtin

testing/test_assertrewrite.py

@@ -412,6 +412,36 @@ def test_rewritten():
         testdir.tmpdir.join("test_newlines.py").write(b, "wb")
         assert testdir.runpytest().ret == 0
 
+
+class TestAssertionRewriteHookDetails(object):
+    def test_loader_is_package_false_for_module(self, testdir):
+        testdir.makepyfile(test_fun="""
+            def test_loader():
+                assert not __loader__.is_package(__name__)
+            """)
+        result = testdir.runpytest()
+        result.stdout.fnmatch_lines([
+            "* 1 passed*",
+        ])
+
+    def test_loader_is_package_true_for_package(self, testdir):
+        testdir.makepyfile(test_fun="""
+            def test_loader():
+                assert not __loader__.is_package(__name__)
+
+            def test_fun():
+                assert __loader__.is_package('fun')
+
+            def test_missing():
+                assert not __loader__.is_package('pytest_not_there')
+            """)
+        pkg = testdir.mkpydir('fun')
+        result = testdir.runpytest()
+        result.stdout.fnmatch_lines([
+            '* 3 passed*',
+        ])
+
+
     @pytest.mark.skipif("sys.version_info[0] >= 3")
     def test_assume_ascii(self, testdir):
         content = "u'\xe2\x99\xa5'"