use specialized Python exception classes

src/Mod/Import/App/AppImportPy.cpp

@@ -350,7 +350,7 @@ static PyObject * importAssembly(PyObject *self, PyObject *args)
                 aReader.SetNameMode(true);
                 aReader.SetLayerMode(true);
                 if (aReader.ReadFile((Standard_CString)(name8bit.c_str())) != IFSelect_RetDone) {
-                    PyErr_SetString(PyExc_Exception, "cannot read STEP file");
+                    PyErr_SetString(PyExc_IOError, "cannot read STEP file");
                     return 0;
                 }
 
@@ -379,7 +379,7 @@ static PyObject * importAssembly(PyObject *self, PyObject *args)
                 aReader.SetNameMode(true);
                 aReader.SetLayerMode(true);
                 if (aReader.ReadFile((Standard_CString)(name8bit.c_str())) != IFSelect_RetDone) {
-                    PyErr_SetString(PyExc_Exception, "cannot read IGES file");
+                    PyErr_SetString(PyExc_IOError, "cannot read IGES file");
                     return 0;
                 }
 
@@ -400,7 +400,7 @@ static PyObject * importAssembly(PyObject *self, PyObject *args)
             }
         }
         else {
-            PyErr_SetString(PyExc_Exception, "no supported file format");
+            PyErr_SetString(PyExc_RuntimeError, "no supported file format");
             return 0;
         }
 
@@ -411,7 +411,7 @@ static PyObject * importAssembly(PyObject *self, PyObject *args)
     }
     catch (Standard_Failure) {
         Handle(Standard_Failure) e = Standard_Failure::Caught();
-        PyErr_SetString(PyExc_Exception, e->GetMessageString());
+        PyErr_SetString(PyExc_RuntimeError, e->GetMessageString());
         return 0;
     }
     PY_CATCH