The import resolution for namespace packages was wrong

With this change we can now include all parents of the script, which will make
relative imports always work.

Now the whole meta_path is scanned and not just importlib's PathFinder.

Fixes #1183.

jedi/_compatibility.py

@@ -34,24 +34,36 @@ class DummyFile(object):
         del self.loader
 
 
-def find_module_py34(string, path=None, full_name=None):
+def find_module_py34(string, path=None, full_name=None, is_global_search=True):
     spec = None
     loader = None
 
-    spec = importlib.machinery.PathFinder.find_spec(string, path)
-    if spec is not None:
-        # We try to disambiguate implicit namespace pkgs with non implicit namespace pkgs
-        if not spec.has_location:
-            full_name = string if not path else full_name
-            implicit_ns_info = ImplicitNSInfo(full_name, spec.submodule_search_locations._path)
-            return None, implicit_ns_info, False
+    for finder in sys.meta_path:
+        if is_global_search and finder != importlib.machinery.PathFinder:
+            p = None
+        else:
+            p = path
+        try:
+            find_spec = finder.find_spec
+        except AttributeError:
+            # These are old-school clases that still have a different API, just
+            # ignore those.
+            continue
+
+        spec = find_spec(string, p)
+        if spec is not None:
+            loader = spec.loader
+            if loader is None and not spec.has_location:
+                # This is a namespace package.
+                full_name = string if not path else full_name
+                implicit_ns_info = ImplicitNSInfo(full_name, spec.submodule_search_locations._path)
+                return None, implicit_ns_info, False
+            break
 
-        # we have found the tail end of the dotted path
-        loader = spec.loader
     return find_module_py33(string, path, loader)
 
 
-def find_module_py33(string, path=None, loader=None, full_name=None):
+def find_module_py33(string, path=None, loader=None, full_name=None, is_global_search=True):
     loader = loader or importlib.machinery.PathFinder.find_module(string, path)
 
     if loader is None and path is None:  # Fallback to find builtins
@@ -104,7 +116,7 @@ def find_module_py33(string, path=None, loader=None, full_name=None):
     return module_file, module_path, is_package
 
 
-def find_module_pre_py33(string, path=None, full_name=None):
+def find_module_pre_py33(string, path=None, full_name=None, is_global_search=True):
     # This import is here, because in other places it will raise a
     # DeprecationWarning.
     import imp