[backends/python] check via pylint

https://bugzilla.gnome.org/show_bug.cgi?id=742658

README

@@ -185,6 +185,7 @@ Dependencies : python, python-dbus, python-simplejson
 
 ### Python
 Dependencies : python, python-dbus
+Optional dependencies : pylint (enabled only if you will pass "pylint" in "options" to dbus service)
 
 ### Ruby
 Dependencies : ruby, ruby-dbus

backends/python/__init__.py

 # gnome code assistance python backend
 # Copyright (C) 2013  Jesse van den Kieboom <jessevdk@gnome.org>
 # Copyright (C) 2014  Elad Alfassa <elad@fedoraproject.org>
+# Copyright (C) 2015  Igor Gnatenko <ignatenko@src.gnome.org>
 #
 # This program is free software; you can redistribute it and/or modify
 # it under the terms of the GNU General Public License as published by
@@ -20,8 +21,50 @@ import ast
 import subprocess
 import re
 
+try:
+    from pylint import lint
+    from pylint.reporters.text import TextReporter
+except ImportError:
+    pass
+
 from gnome.codeassistance import transport, types
 
+class PyLint(object):
+    def __init__(self, data_path):
+        self.diagnostics = []
+        self.data_path = data_path
+
+    def write(self, st):
+        if st != "\n" and not st.startswith("*"):
+            result = st.split(":")
+            col = int(result[1]) + 1
+            loc = types.SourceLocation(line=result[0], column=col)
+
+            """
+            * (C) convention, for programming standard violation
+            * (R) refactor, for bad code smell
+            * (W) warning, for python specific problems
+            * (E) error, for much probably bugs in the code
+            * (F) fatal, if an error occurred which prevented pylint from doing
+            further processing.
+            """
+            if result[2] == "C" or result[2] == "R" or result[2] == "W":
+                severity = types.Diagnostic.Severity.INFO
+            else:
+                severity = types.Diagnostic.Severity.ERROR
+
+            self.diagnostics.append(
+                types.Diagnostic(severity=severity,
+                                 locations=[loc.to_range()],
+                                 message=result[3]))
+
+    def run(self):
+        args = [self.data_path, "-r", "n",
+                "--msg-template='{line}:{column}:{C}:{msg_id} {msg}'"]
+        lint.Run(args, reporter=TextReporter(self), exit=False)
+        return self.diagnostics
+
+
 class Service(transport.Service):
     language = 'python'
 
@@ -54,6 +97,14 @@ class Service(transport.Service):
             # PEP8 is not installed. Do nothing.
             pass
 
+        if "pylint" in options and options["pylint"]:
+            pylint = PyLint(doc.data_path)
+            diagnostics = pylint.run()
+
+            for diag in diagnostics:
+                doc.diagnostics.append(diag)
+
+
 class Document(transport.Document, transport.Diagnostics):
     pass