replwrap module requires path to *real* pexpect path to find bashrc.sh

Thanks to @auneri for finding fix to #144.

This names and exports pexpect's __file__.

Closes #144.

metakernel/pexpect.py

@@ -2,7 +2,7 @@
 from __future__ import absolute_import
 import os
 import signal
-from pexpect import is_executable_file, EOF, TIMEOUT
+from pexpect import is_executable_file, EOF, TIMEOUT, __file__ as PEXPECT_DIR
 
 try:
     from pexpect import spawn as pty_spawn

metakernel/replwrap.py

@@ -229,7 +229,7 @@ def bash(command="bash", prompt_regex=re.compile('[$#]')):
     extra_init_cmd = "export PAGER=cat"
 
     # Make sure the bash shell has a valid ending character.
-    bashrc = os.path.join(os.path.dirname(pexpect.__file__), 'bashrc.sh')
+    bashrc = os.path.join(os.path.dirname(pexpect.PEXPECT_DIR), 'bashrc.sh')
     child = pexpect.spawn(command, ['--rcfile', bashrc], echo=False,
                           encoding='utf-8')