Replace deprecated pipes with shlex

pubs/plugs/alias/alias.py

@@ -1,7 +1,7 @@
 import shlex
 import subprocess
 import argparse
-from pipes import quote as shell_quote
+from shlex import quote as shell_quote
 
 from ...plugins import PapersPlugin
 from ...pubs_cmd import execute

pubs/plugs/git/git.py

@@ -2,7 +2,7 @@ import os
 import sys
 import argparse
 from subprocess import Popen, PIPE, STDOUT
-from pipes import quote as shell_quote
+from shlex import quote as shell_quote
 
 from ... import uis
 from ...plugins import PapersPlugin