Fix exception formatting while importing test modules

Fix pytest-dev#2336

Author: nicoddemus

CHANGELOG.rst

@@ -5,7 +5,10 @@
   than ValueErrors in the ``fileno`` method (`#2276`_).
   Thanks `@metasyn`_ for the PR.
 
-*
+* Fix exception formatting while importing modules when the exception message
+  contains non-ascii characters (`#2336`_).
+  Thanks `@fabioz`_ for the report and `@nicoddemus`_ for the PR.
+
 
 *
 
@@ -14,10 +17,12 @@
 *
 
 
+.. _@fabioz: https://github.com/fabioz
 .. _@metasyn: https://github.com/metasyn
 
 
 .. _#2276: https://github.com/pytest-dev/pytest/issues/2276
+.. _#2336: https://github.com/pytest-dev/pytest/issues/2336
 
 
 3.0.7 (2017-03-14)

_pytest/compat.py

@@ -237,5 +237,7 @@ def safe_str(v):
         try:
             return str(v)
         except UnicodeError:
+            if not isinstance(v, unicode):
+                v = unicode(v)
             errors = 'replace'
             return v.encode('ascii', errors)

_pytest/python.py

@@ -19,7 +19,7 @@
     isclass, isfunction, is_generator, _escape_strings,
     REGEX_TYPE, STRING_TYPES, NoneType, NOTSET,
     get_real_func, getfslineno, safe_getattr,
-    getlocation, enum,
+    safe_str, getlocation, enum,
 )
 
 cutdir1 = py.path.local(pluggy.__file__.rstrip("oc"))
@@ -437,7 +437,7 @@ def _importtestmodule(self):
             if self.config.getoption('verbose') < 2:
                 exc_info.traceback = exc_info.traceback.filter(filter_traceback)
             exc_repr = exc_info.getrepr(style='short') if exc_info.traceback else exc_info.exconly()
-            formatted_tb = py._builtin._totext(exc_repr)
+            formatted_tb = safe_str(exc_repr)
             raise self.CollectError(
                 "ImportError while importing test module '{fspath}'.\n"
                 "Hint: make sure your test modules/packages have valid Python names.\n"

testing/python/collect.py

@@ -105,6 +105,24 @@ def test_show_traceback_import_error(self, testdir, verbose):
                 assert name not in stdout
 
 
+    def test_show_traceback_import_error_unicode(self, testdir):
+        """Import errors when collecting modules should display the traceback (#1976).
+
+        With low verbosity we omit pytest and internal modules, otherwise show all traceback entries.
+        """
+        testdir.makepyfile(u"""
+            # -*- coding: utf-8 -*-
+            raise ImportError(u'Something bad happened ☺')
+        """)
+        result = testdir.runpytest()
+        result.stdout.fnmatch_lines([
+            "ImportError while importing test module*",
+            "Traceback:",
+            "*raise ImportError*Something bad happened*",
+        ])
+        assert result.ret == 2
+
+
 class TestClass:
     def test_class_with_init_warning(self, testdir):
         testdir.makepyfile("""