Merge pull request #3613 from asottile/module_spec_warnings

Fix `ImportWarning` triggered by explicit relative imports

changelog/3061.bugfix.rst

@@ -0,0 +1 @@
+Fix ``ImportWarning`` triggered by explicit relative imports in assertion-rewritten package modules.

src/_pytest/assertion/rewrite.py

@@ -45,6 +45,14 @@ else:
         return ast.Call(a, b, c, None, None)
 
 
+if sys.version_info >= (3, 4):
+    from importlib.util import spec_from_file_location
+else:
+
+    def spec_from_file_location(*_, **__):
+        return None
+
+
 class AssertionRewritingHook(object):
     """PEP302 Import hook which rewrites asserts."""
 
@@ -213,6 +221,8 @@ class AssertionRewritingHook(object):
             # Normally, this attribute is 3.2+.
             mod.__cached__ = pyc
             mod.__loader__ = self
+            # Normally, this attribute is 3.4+
+            mod.__spec__ = spec_from_file_location(name, co.co_filename, loader=self)
             py.builtin.exec_(co, mod.__dict__)
         except:  # noqa
             if name in sys.modules:

tox.ini

@@ -204,9 +204,6 @@ filterwarnings =
     ignore:.*type argument to addoption.*:DeprecationWarning
     # produced by python >=3.5 on execnet (pytest-xdist)
     ignore:.*inspect.getargspec.*deprecated, use inspect.signature.*:DeprecationWarning
-    # ignore warning about package resolution using __spec__ or __package__
-    # should be a temporary solution, see #3061 for discussion
-    ignore:.*can't resolve package from __spec__ or __package__.*:ImportWarning
 
 [flake8]
 max-line-length = 120