Actually, just keep the old behaviour for now.

code/Common/BaseImporter.cpp

@@ -130,14 +130,9 @@ aiScene *BaseImporter::ReadFile(Importer *pImp, const std::string &pFile, IOSyst
         // passes scale into ScaleProcess
         UpdateImporterScale(pImp);
 
-    } catch( const DeadlyImportError& err )    {
+    } catch( const std::exception &err ) {
         // extract error description
         m_ErrorText = err.what();
-        ASSIMP_LOG_ERROR(m_ErrorText.c_str());
-        m_Exception = std::current_exception();
-        return nullptr;
-    } catch( const std::exception& err )    {
-        m_ErrorText = "Internal error";
         ASSIMP_LOG_ERROR(err.what());
         m_Exception = std::current_exception();
         return nullptr;

code/Common/Importer.h

@@ -97,9 +97,8 @@ public:
     /** The imported data, if ReadFile() was successful, nullptr otherwise. */
     aiScene* mScene;
 
-    /** The error description, if there was one. In the case of a
-     *  failure not caused by a DeadlyImportError, mInternalException will
-     *  carry the full details and this will be just "Internal error". */
+    /** The error description, if there was one. In the case of an exception,
+     *  mException will carry the full details. */
     std::string mErrorString;
 
     /** Any exception which occurred */