oven: print the original tracebac in build step errors

cerbero/build/oven.py

@@ -18,6 +18,7 @@
 
 import tempfile
 import shutil
+import traceback
 
 from cerbero.errors import BuildStepError, FatalError
 from cerbero.build.recipe import Recipe, BuildSteps
@@ -103,9 +104,8 @@ class Oven (object):
                 self.cookbook.update_step_status(recipe.name, step)
             except FatalError:
                 self._handle_build_step_error(recipe, step)
-            except Exception, ex:
-                raise FatalError(_("Error performing step %s: %s") % (step,
-                                  ex))
+            except Exception:
+                raise BuildStepError(recipe, step, traceback.format_exc())
         self.cookbook.update_build_status(recipe.name, False)
 
         if self.missing_files:

cerbero/errors.py

@@ -47,9 +47,9 @@ class CommandError(CerberoException):
 
 class BuildStepError(CerberoException):
 
-    def __init__(self, recipe, step):
+    def __init__(self, recipe, step, trace=''):
         CerberoException.__init__(self, _("Recipe '%s' failed at the build "
-            "step '%s'") % (recipe, step))
+            "step '%s'\n%s") % (recipe, step, trace))
 
 
 class RecipeNotFoundError(CerberoException):