print traceback on failed import (#537)

include/pybind11/common.h

diff --git a/include/pybind11/common.h b/include/pybind11/common.h
index 7da4215..74dcbd9 100644
--- a/include/pybind11/common.h
+++ b/include/pybind11/common.h
@@ -511,7 +511,6 @@
 PYBIND11_RUNTIME_EXCEPTION(index_error, PyExc_IndexError)
 PYBIND11_RUNTIME_EXCEPTION(key_error, PyExc_KeyError)
 PYBIND11_RUNTIME_EXCEPTION(value_error, PyExc_ValueError)
-PYBIND11_RUNTIME_EXCEPTION(import_error, PyExc_ImportError)
 PYBIND11_RUNTIME_EXCEPTION(type_error, PyExc_TypeError)
 PYBIND11_RUNTIME_EXCEPTION(cast_error, PyExc_RuntimeError) /// Thrown when pybind11::cast or handle::call fail due to a type casting error
 PYBIND11_RUNTIME_EXCEPTION(reference_cast_error, PyExc_RuntimeError) /// Used internally

include/pybind11/pybind11.h

diff --git a/include/pybind11/pybind11.h b/include/pybind11/pybind11.h
index 37d6139..c88273d 100644
--- a/include/pybind11/pybind11.h
+++ b/include/pybind11/pybind11.h
@@ -580,7 +580,7 @@
     static module import(const char *name) {
         PyObject *obj = PyImport_ImportModule(name);
         if (!obj)
-            throw import_error("Module \"" + std::string(name) + "\" not found!");
+            throw error_already_set();
         return reinterpret_steal<module>(obj);
     }
 
@@ -1495,7 +1495,7 @@
     } else {
         try {
             file = module::import("sys").attr("stdout");
-        } catch (const import_error &) {
+        } catch (const error_already_set &) {
             /* If print() is called from code that is executed as
                part of garbage collection during interpreter shutdown,
                importing 'sys' can fail. Give up rather than crashing the