shiboken: warn if the signature module fails to initialize

There are setup errors that fail to initialize the signature module
correctly. This is for instance possible if packaging puts the shiboken2
module somewhere into the path, but the binary cannot be reached,
because shiboken2 also exists as a dictionary.

Task-number: PYSIDE-1352
Change-Id: I679d6855c87093b946cfbaeb063c10d45b00c8ad
Reviewed-by: Cristian Maureira-Fredes <cristian.maureira-fredes@qt.io>

1 files changed, 15 insertions, 1 deletions

diff --git a/sources/pyside2/PySide2/__init__.py.in b/sources/pyside2/PySide2/__init__.py.in
index f860c6ac9..5c33c57a0 100644
--- a/sources/pyside2/PySide2/__init__.py.in
+++ b/sources/pyside2/PySide2/__init__.py.in
@@ -1,6 +1,7 @@
 from __future__ import print_function
 import os
 import sys
+from textwrap import dedent
 
 __all__ = list("Qt" + body for body in
     "@all_module_shortnames@"
@@ -62,7 +63,20 @@ def _setupQtDirectories():
         raise
 
     #   Trigger signature initialization.
-    type.__signature__
+    try:
+        type.__signature__
+    except AttributeError:
+        print(dedent('''\
+            {stars}
+            PySide2/__init__.py: The `signature` module was not initialized.
+            This libshiboken module was loaded from
+
+            "{shiboken2.__file__}".
+
+            Please make sure that this is the real shiboken2 binary and not just a folder.
+            {stars}
+            ''').format(stars=79*"*", **locals()), file=sys.stderr)
+        raise
 
     if sys.platform == 'win32':
         # PATH has to contain the package directory, otherwise plugins