Add standard error to exception message

The rationale is that when castxml has an error it raises a RuntimeError to the user with the message.
However, the message only contains the stdout from castxml - this makes the RuntimeError contain no information about what actually went wrong.
This change allows the user to add error handling to their applications based on what went wrong with castxml (such as changing their include directories, etc)

Author: allisonChilton

src/pygccxml/parser/source_reader.py

@@ -235,7 +235,8 @@ def create_xml_file(self, source_file, destination=None):
         process = subprocess.Popen(
             args=command_line,
             shell=True,
-            stdout=subprocess.PIPE)
+            stdout=subprocess.PIPE,
+            stderr=subprocess.PIPE)
 
         try:
             results = []
@@ -246,9 +247,12 @@ def create_xml_file(self, source_file, destination=None):
             for line in process.stdout.readlines():
                 if line.strip():
                     results.append(line.rstrip())
+            for line in process.stderr.readlines():
+                if line.strip():
+                    results.append(line.rstrip())
 
             exit_status = process.returncode
-            msg = os.linesep.join([str(s) for s in results])
+            msg = os.linesep.join([str(s.decode()) for s in results])
             if self.__config.ignore_gccxml_output:
                 if not os.path.isfile(xml_file):
                     raise RuntimeError(
@@ -257,18 +261,17 @@ def create_xml_file(self, source_file, destination=None):
                         ": %s status:%s" %
                         (msg, exit_status))
             else:
-                if msg or exit_status or not \
-                        os.path.isfile(xml_file):
-                    if not os.path.isfile(xml_file):
-                        raise RuntimeError(
-                            "Error occurred while running " +
-                            self.__config.xml_generator.upper() +
-                            " xml file does not exist")
-                    else:
-                        raise RuntimeError(
-                            "Error occurred while running " +
-                            self.__config.xml_generator.upper() +
-                            ": %s status:%s" % (msg, exit_status))
+                if msg or exit_status:
+                    raise RuntimeError(
+                        "Error occurred while running " +
+                        self.__config.xml_generator.upper() +
+                        ": %s status:%s" % (msg, exit_status))
+                if not os.path.isfile(xml_file):
+                    raise RuntimeError(
+                        "Error occurred while running " +
+                        self.__config.xml_generator.upper() +
+                        " xml file does not exist")
+
         except Exception:
             utils.remove_file_no_raise(xml_file, self.__config)
             raise

tests/test_source_reader.py

@@ -4,6 +4,7 @@
 # See http://www.boost.org/LICENSE_1_0.txt
 
 import platform
+import os
 
 import pytest
 
@@ -35,3 +36,15 @@ def test_compound_argument_type(global_ns):
     do_smth = global_ns.calldefs('do_smth')
     assert do_smth is not None
     do_smth.function_type()
+
+
+def test_stderr_present_and_readable():
+    with open(os.path.join('tests', 'data', TEST_FILES[0]), 'r') as f:
+        source_str = f.read()
+
+    err_str = "add some stuff that should not compile"
+    source_str += err_str
+    config = autoconfig.cxx_parsers_cfg.config.clone()
+    with pytest.raises(RuntimeError) as e_context:
+        parser.parse_string(source_str, config)
+    assert err_str in str(e_context)