sip_to_pjsip: improve ability to parse input files

General improvements to SIP to PJSIP conversion utility:

1) track default section of input file to allow parsing
   an include file that doesn't specify a [section]

2) informatively handle case of assignment without [section]

3) correctly handle getting sections from included files
   - [section]'s are inherited by included file

4) provide null string as default transport bind ip

5) gracefully handle missing portions of registration string

6) denote steps of operation during conversion and confirm
   top level files as a convenience

ASTERISK-24474 #close
Review: https://reviewboard.asterisk.org/r/4280/
Reported by: John Kiniston
........

Merged revisions 430469 from http://svn.asterisk.org/svn/asterisk/branches/13


git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@430470 65c4cc65-6c06-0410-ace0-fbb531ad65f3

contrib/scripts/sip_to_pjsip/astconfigparser.py

@@ -1,4 +1,5 @@
 import re
+import itertools
 
 from astdicts import OrderedDict
 from astdicts import MultiOrderedDict
@@ -331,7 +332,9 @@ class MultiOrderedConfigParser:
         res = sections[key] if key in sections else []
         searched.append(self)
         if self._includes:
-            res += self._includes.get_sections(key, attr, searched)
+            res.extend(list(itertools.chain(*[
+                incl.get_sections(key, attr, searched)
+                for incl in self._includes.itervalues()])))
         if self._parent:
             res += self._parent.get_sections(key, attr, searched)
         return res
@@ -415,15 +418,15 @@ class MultiOrderedConfigParser:
         else:
             self.defaults(section)[0][key] = val
 
-    def read(self, filename):
+    def read(self, filename, sect=None):
         """Parse configuration information from a file"""
         try:
             with open(filename, 'rt') as config_file:
-                self._read(config_file)
+                self._read(config_file, sect)
         except IOError:
             print "Could not open file ", filename, " for reading"
 
-    def _read(self, config_file):
+    def _read(self, config_file, sect):
         """Parse configuration information from the config_file"""
         is_comment = False  # used for multi-lined comments
         for line in config_file:
@@ -435,7 +438,7 @@ class MultiOrderedConfigParser:
             include_name = try_include(line)
             if include_name:
                 parser = self.add_include(include_name)
-                parser.read(include_name)
+                parser.read(include_name, sect)
                 continue
 
             section, is_template, templates = try_section(line)
@@ -447,6 +450,8 @@ class MultiOrderedConfigParser:
                 continue
 
             key, val = try_option(line)
+            if sect is None:
+                raise Exception("Section not defined before assignment")
             sect[key] = val
 
     def write(self, config_file):