print caught exceptions when (de)serializing (#332)

* print caught exceptions when (de)serializing

* include trace in error message

Co-authored-by: David Little <david.frank.little@gmail.com>

* print backtrace

* typo

* wrap sprint in try-catch block and print in debug

---------

Co-authored-by: David Little <david.frank.little@gmail.com>

src/cpython/jlwrap.jl

@@ -206,6 +206,12 @@ function _pyjl_serialize(self::PyPtr, ::PyPtr)
         return PyBytes_FromStringAndSize(pointer(b), sizeof(b))
     catch e
         PyErr_SetString(POINTERS.PyExc_Exception, "error serializing this value")
+        # wrap sprint in another try-catch block to prevent this function from throwing
+        try
+            @debug "Caught exception $(sprint(showerror, e, catch_backtrace()))"
+        catch e2
+            @debug "Error printing exception: $e2"
+        end
         return PyNULL
     end
 end
@@ -221,6 +227,12 @@ function _pyjl_deserialize(t::PyPtr, v::PyPtr)
         return PyJuliaValue_New(t, x)
     catch e
         PyErr_SetString(POINTERS.PyExc_Exception, "error deserializing this value")
+        # wrap sprint in another try-catch block to prevent this function from throwing
+        try
+            @debug "Caught exception $(sprint(showerror, e, catch_backtrace()))"
+        catch e2
+            @debug "Error printing exception: $e2"
+        end
         return PyNULL
     end
 end