Ensure test_run.py works when system-wide bashrc produces output

The --rcfile option to bash does not prevent the system-wide
/etc/bash.bashrc script from running (contrary to the Debian man-page).
This causes test_run.py to fail when the system-wide script produces
output (as is the case in an Ubuntu image where the regular user belongs
to the "sudo" group and the system-wide script produces an informational
message about sudo usage).

Rather than rely on --rcfile, this patch changes the test to use --norc
(which does suppress the execution of the system-wide bashrc), and
changes PS1 via the inherited environment instead (this also slightly
simplifies the fixture setup too as tempfile is no longer required).

tests/test_run.py

@@ -22,7 +22,6 @@
 import pexpect
 import unittest
 import subprocess
-import tempfile
 import sys
 import os
 from . import PexpectTestCase
@@ -59,15 +58,10 @@ class RunFuncTestCase(PexpectTestCase.PexpectTestCase):
     prep_subprocess_out = staticmethod(lambda x: x)
 
     def setUp(self):
-        fd, self.rcfile = tempfile.mkstemp()
-        os.write(fd, b'PS1=GO: \n')
-        os.close(fd)
+        self.runenv = os.environ.copy()
+        self.runenv['PS1'] = 'GO:'
         super(RunFuncTestCase, self).setUp()
 
-    def tearDown(self):
-        os.unlink(self.rcfile)
-        super(RunFuncTestCase, self).tearDown()
-
     def test_run_exit(self):
         (data, exitstatus) = self.runfunc(sys.executable + ' exit1.py', withexitstatus=1)
         assert exitstatus == 1, "Exit status of 'python exit1.py' should be 1."
@@ -106,9 +100,10 @@ def test_run_event_as_string(self):
         ]
 
         (data, exitstatus) = pexpect.run(
-            'bash --rcfile {0}'.format(self.rcfile),
+            'bash --norc',
             withexitstatus=True,
             events=events,
+            env=self.runenv,
             timeout=10)
         assert exitstatus == 0
 
@@ -118,9 +113,10 @@ def test_run_event_as_function(self):
         ]
 
         (data, exitstatus) = pexpect.run(
-            'bash --rcfile {0}'.format(self.rcfile),
+            'bash --norc',
             withexitstatus=True,
             events=events,
+            env=self.runenv,
             timeout=10)
         assert exitstatus == 0
 
@@ -130,18 +126,20 @@ def test_run_event_as_method(self):
         ]
 
         (data, exitstatus) = pexpect.run(
-            'bash --rcfile {0}'.format(self.rcfile),
+            'bash --norc',
             withexitstatus=True,
             events=events,
+            env=self.runenv,
             timeout=10)
         assert exitstatus == 0
 
     def test_run_event_typeerror(self):
         events = [('GO:', -1)]
         with self.assertRaises(TypeError):
-            pexpect.run('bash --rcfile {0}'.format(self.rcfile),
+            pexpect.run('bash --norc',
                         withexitstatus=True,
                         events=events,
+                        env=self.runenv,
                         timeout=10)
 
     def _method_events_callback(self, values):