Test and fix for a better error message on failing imports

3 files changed, 9 insertions, 1 deletions

diff --git a/rpython/flowspace/flowcontext.py b/rpython/flowspace/flowcontext.py
index 2144ba4a27..c204cb5f98 100644
--- a/rpython/flowspace/flowcontext.py
+++ b/rpython/flowspace/flowcontext.py
@@ -1207,7 +1207,8 @@ class Raise(FlowSignal):
     def nomoreblocks(self, ctx):
         w_exc = self.w_exc
         if w_exc.w_type == const(ImportError):
-            msg = 'import statement always raises %s' % self
+            msg = 'ImportError is raised in RPython: %s' % (
+                getattr(w_exc.w_value, 'value', '<not a constant message>'),)
             raise ImportError(msg)
         link = Link([w_exc.w_type, w_exc.w_value], ctx.graph.exceptblock)
         ctx.recorder.crnt_block.closeblock(link)
diff --git a/rpython/flowspace/test/cant_import.py b/rpython/flowspace/test/cant_import.py
new file mode 100644
index 0000000000..174bd09444
--- /dev/null
+++ b/rpython/flowspace/test/cant_import.py
@@ -0,0 +1 @@
+raise ImportError("some explanation here")
diff --git a/rpython/flowspace/test/test_objspace.py b/rpython/flowspace/test/test_objspace.py
index db4137d50d..37f8ef3d7e 100644
--- a/rpython/flowspace/test/test_objspace.py
+++ b/rpython/flowspace/test/test_objspace.py
@@ -816,6 +816,12 @@ class TestFlowObjSpace(Base):
             from rpython import this_does_not_exist
         py.test.raises(ImportError, 'self.codetest(f)')
 
+    def test_importerror_3(self):
+        def f():
+            import rpython.flowspace.test.cant_import
+        e = py.test.raises(ImportError, 'self.codetest(f)')
+        assert "some explanation here" in str(e.value)
+
     def test_relative_import(self):
         def f():
             from ..objspace import build_flow