run-tests: drop fallback for sysconfig for pre-py2.7

tests/run-tests.py

@@ -58,11 +58,7 b' import signal'
 import socket
 import subprocess
 import sys
-try:
-    import sysconfig
-except ImportError:
-    # sysconfig doesn't exist in Python 2.6
-    sysconfig = None
+import sysconfig
 import tempfile
 import threading
 import time
@@ -882,8 +878,7 b' class Test(unittest.TestCase):'
             offset = '' if i == 0 else '%s' % i
             env["HGPORT%s" % offset] = '%s' % (self._startport + i)
         env = os.environ.copy()
-        if sysconfig is not None:
-            env['PYTHONUSERBASE'] = sysconfig.get_config_var('userbase')
+        env['PYTHONUSERBASE'] = sysconfig.get_config_var('userbase')
         env['HGEMITWARNINGS'] = '1'
         env['TESTTMP'] = self._testtmp
         env['HOME'] = self._testtmp