Add `wait` optional argument to `hooks.editor`

subprocess.Popen is used instead of os.system in order to spawn editor
process in non-blocking manner.

IPython/core/hooks.py

@@ -42,6 +42,7 b' somewhere in your configuration files or ipython command line.'
 #*****************************************************************************
 
 import os, bisect
+import subprocess
 import sys
 
 from IPython.core.error import TryNext
@@ -54,7 +55,7 b" __all__ = ['editor', 'fix_error_editor', 'synchronize_with_editor',"
            'show_in_pager','pre_prompt_hook',
            'pre_run_code_hook', 'clipboard_get']
 
-def editor(self,filename, linenum=None):
+def editor(self, filename, linenum=None, wait=True):
     """Open the default editor at the given filename and linenumber.
 
     This is IPython's default editor hook, you can use it as an example to
@@ -76,7 +77,9 b' def editor(self,filename, linenum=None):'
         editor = '"%s"' % editor
 
     # Call the actual editor
-    if os.system('%s %s %s' % (editor,linemark,filename)) != 0:
+    proc = subprocess.Popen('%s %s %s' % (editor, linemark, filename),
+                            shell=True)
+    if wait and proc.wait() != 0:
         raise TryNext()
 
 import tempfile