Introduce record_testsuite_property fixture

This exposes the functionality introduced in fa6acdc as a session-scoped fixture.

Plugins that want to remain compatible with the `xunit2`
standard should use this fixture instead of `record_property`.

Fix #5202

src/_pytest/junitxml.py

@@ -345,6 +345,45 @@ def record_xml_attribute(request):
     return attr_func
 
 
+def _check_record_param_type(param, v):
+    """Used by record_testsuite_property to check that the given parameter name is of the proper
+    type"""
+    __tracebackhide__ = True
+    if not isinstance(v, six.string_types):
+        msg = "{param} parameter needs to be a string, but {g} given"
+        raise TypeError(msg.format(param=param, g=type(v).__name__))
+
+
+@pytest.fixture(scope="session")
+def record_testsuite_property(request):
+    """
+    Records a new ``<property>`` tag as child of the root ``<testsuite>``. This is suitable to
+    writing global information regarding the entire test suite, and is compatible with ``xunit2`` JUnit family.
+
+    This is a ``session``-scoped fixture which is called with ``(name, value)``. Example:
+
+    .. code-block:: python
+
+        def test_foo(record_testsuite_property):
+            record_testsuite_property("ARCH", "PPC")
+            record_testsuite_property("STORAGE_TYPE", "CEPH")
+
+    ``name`` must be a string, ``value`` will be converted to a string and properly xml-escaped.
+    """
+
+    __tracebackhide__ = True
+
+    def record_func(name, value):
+        """noop function in case --junitxml was not passed in the command-line"""
+        __tracebackhide__ = True
+        _check_record_param_type("name", name)
+
+    xml = getattr(request.config, "_xml", None)
+    if xml is not None:
+        record_func = xml.add_global_property  # noqa
+    return record_func
+
+
 def pytest_addoption(parser):
     group = parser.getgroup("terminal reporting")
     group.addoption(
@@ -444,6 +483,7 @@ class LogXML(object):
         self.node_reporters = {}  # nodeid -> _NodeReporter
         self.node_reporters_ordered = []
         self.global_properties = []
+
         # List of reports that failed on call but teardown is pending.
         self.open_reports = []
         self.cnt_double_fail_tests = 0
@@ -632,7 +672,9 @@ class LogXML(object):
         terminalreporter.write_sep("-", "generated xml file: %s" % (self.logfile))
 
     def add_global_property(self, name, value):
-        self.global_properties.append((str(name), bin_xml_escape(value)))
+        __tracebackhide__ = True
+        _check_record_param_type("name", name)
+        self.global_properties.append((name, bin_xml_escape(value)))
 
     def _get_global_properties_node(self):
         """Return a Junit node containing custom properties, if any.