jp (pubsub): new "transform" command:

This command allows to pass all requested items through an external command to filter them (i.e. modify their content).
- created new jp.xml_tools module with some common functions (like lxml parsing)
- new EXIT code EXIT_CMD_ERROR (used when a third party utility returns an error)

sat_frontends/jp/xml_tools.py

@@ -0,0 +1,62 @@
+#!/usr/bin/env python2
+# -*- coding: utf-8 -*-
+
+# jp: a SàT command line tool
+# Copyright (C) 2009-2019 Jérôme Poisson (goffi@goffi.org)
+
+# This program is free software: you can redistribute it and/or modify
+# it under the terms of the GNU Affero General Public License as published by
+# the Free Software Foundation, either version 3 of the License, or
+# (at your option) any later version.
+
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU Affero General Public License for more details.
+
+# You should have received a copy of the GNU Affero General Public License
+# along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+from sat.core.i18n import _
+from sat_frontends.jp.constants import Const as C
+
+def etreeParse(cmd, raw_xml):
+    """Import lxml and parse raw XML
+
+    @param cmd(CommandBase): current command instance
+    @param raw_xml(file, str): an XML bytestring, string or file-like object
+    @return (tuple(etree.Element, module): parsed element, etree module
+    """
+    try:
+        from lxml import etree
+    except ImportError:
+        cmd.disp(
+            u'lxml module must be installed, please install it with "pip install lxml"',
+            error=True,
+        )
+        cmd.host.quit(C.EXIT_ERROR)
+    try:
+        if isinstance(raw_xml, basestring):
+            parser = etree.XMLParser(remove_blank_text=True)
+            element = etree.fromstring(raw_xml, parser)
+        else:
+            element = etree.parse(raw_xml).getroot()
+    except Exception as e:
+        cmd.parser.error(
+            _(u"Can't parse the payload XML in input: {msg}").format(msg=e)
+        )
+    return element, etree
+
+def getPayload(cmd, element):
+    """Retrieve payload element and exit with and error if not found
+
+    @param element(etree.Element): root element
+    @return element(etree.Element): payload element
+    """
+    if element.tag in ("item", "{http://jabber.org/protocol/pubsub}item"):
+        if len(element) > 1:
+            cmd.disp(_(u"<item> can only have one child element (the payload)"),
+                     error=True)
+            cmd.host.quit(C.EXIT_DATA_ERROR)
+        element = element[0]
+    return element