python: also catch general c++ exceptions

they might be thrown from third-party code (notably Ogre in the ovis
module).
While Linux is kind enough to print them, they cause instant termination
on Windows.
Arguably, they do not origin from OpenCV itself, but still this helps
understanding what went wrong when calling an OpenCV function.

modules/core/include/opencv2/core/bindings_utils.hpp

@@ -8,6 +8,8 @@
 #include <opencv2/core/async.hpp>
 #include <opencv2/core/detail/async_promise.hpp>
 
+#include <stdexcept>
+
 namespace cv { namespace utils {
 //! @addtogroup core_utils
 //! @{
@@ -113,6 +115,12 @@ String dumpRange(const Range& argument)
     }
 }
 
+CV_WRAP static inline
+void testRaiseGeneralException()
+{
+    throw std::runtime_error("exception text");
+}
+
 CV_WRAP static inline
 AsyncArray testAsyncArray(InputArray argument)
 {

modules/python/src2/cv2.cpp

@@ -206,6 +206,11 @@ catch (const cv::Exception &e) \
 { \
     pyRaiseCVException(e); \
     return 0; \
+} \
+catch (const std::exception &e) \
+{ \
+    PyErr_SetString(opencv_error, e.what()); \
+    return 0; \
 }
 
 using namespace cv;

modules/python/test/test_misc.py

@@ -47,6 +47,12 @@ class Bindings(NewOpenCVTests):
         boost.getMaxDepth()  # from ml::DTrees
         boost.isClassifier()  # from ml::StatModel
 
+    def test_raiseGeneralException(self):
+        with self.assertRaises((cv.error,),
+                            msg='C++ exception is not propagated to Python in the right way') as cm:
+            cv.utils.testRaiseGeneralException()
+        self.assertEqual(str(cm.exception), 'exception text')
+
     def test_redirectError(self):
         try:
             cv.imshow("", None)  # This causes an assert