Attempting to patch terminal only if terminalreporter is available

This fixes the flag "--paste=all" when running tests with xdist, as slaves would
attempt to patch a non-existing terminal during pytest_configure. Only the master
node has a terminalreporter installed.

--HG--
branch : pastebin-xdist

_pytest/pastebin.py

@@ -14,8 +14,12 @@ def pytest_addoption(parser):
 @pytest.mark.trylast
 def pytest_configure(config):
     if config.option.pastebin == "all":
-        config._pastebinfile = tempfile.TemporaryFile('w+')
         tr = config.pluginmanager.getplugin('terminalreporter')
+        # if no terminal reporter plugin is present, nothing we can do here;
+        # this can happen when this function executes in a slave node
+        # when using pytest-xdist, for example
+        if tr is not None:
+            config._pastebinfile = tempfile.TemporaryFile('w+')
             oldwrite = tr._tw.write
             def tee_write(s, **kwargs):
                 oldwrite(s, **kwargs)