Making conftest import failures easier to debug

AUTHORS

@@ -59,6 +59,7 @@ Jaap Broekhuizen
 Jan Balster
 Janne Vanhala
 Jason R. Coombs
+Javier Domingo Cansino
 John Towler
 Joshua Bronson
 Jurko Gospodnetić

CHANGELOG.rst

@@ -14,7 +14,7 @@
   level an error will be raised during collection.
   Thanks `@omarkohl`_ for the complete PR (`#1519`_).
 
-*
+* Fix (`1516`_): ConftestImportFailure now shows the traceback
 
 **Incompatible changes**
 

_pytest/config.py

@@ -25,6 +25,12 @@ class ConftestImportFailure(Exception):
         self.path = path
         self.excinfo = excinfo
 
+    def __str__(self):
+        etype, evalue, etb = self.excinfo
+        formatted = traceback.format_tb(etb)
+        # The level of the tracebacks we want to print is hand crafted :(
+        return repr(evalue) + '\n' + ''.join(formatted[2:])
+
 
 def main(args=None, plugins=None):
     """ return exit code, after performing an in-process test run.