Separate which tests into test_which.py
Expand on tests/test_which.py

Mainly, regarding os.defpath, os.environ['PATH'],
absolute, relative, and symlinks.
Provide new 'is_exe' function used by 'which'

As noted by bug report http://bugs.python.org/issue14706,

"This is not a Python bug. os.access() is just a wrapper
 around the POSIX access() function"

http://pubs.opengroup.org/onlinepubs/9699919799/functions/faccessat.html

""" If any access permissions are checked, each shall be
    checked individually, as described in XBD File Access
    Permissions, except that where that description refers
    to execute permission for a process with appropriate
    privileges, an implementation may indicate success for
    X_OK even if execute permission is not granted to any
    user.
"""
Fixing various prompt issues with bash ReplWrapper

allow matching a regular expression,
use setUp and tearDown to putenv & getenv PS1, PS2
unset PROMPT_COMMAND
syntaxerr: missing r'literal' for unset PS1
PR #66: TypeError thrown by spawnu.readline()

Submitted by @auntieNeo, fixes exception, "TypeError:
got <type 'str'> ('\r\n') as pattern" in spawnu.readline().

Bytes b'\r\n' was concatenated to u'unicode', causing an
exception to be thrown when using readline().
Minor fixes for replwrap tests
Make execute permission check more explicit
Merge pull request #71 from pexpect/replwrap-test-fixes

Fixing various prompt issues with bash ReplWrapper
Merge pull request #70 from pexpect/more-exacting-which

new function is_exe() makes existing which() more correct
Improve EOF through test -> interact -> echo_prompt
Document and detect EOF condition in interact()
python3.2 accommodations
For python3, exceptions should use "as err", not ", err"