doc: Cope with Sphinx logging deprecations

Recent versions of sphinx will emit messages like:

  doc/sphinx/kerneldoc.py:103:
     RemovedInSphinx20Warning: app.warning() is now deprecated.
     Use sphinx.util.logging instead.

Switch to sphinx.util.logging to make this unsightly message go away.
Alas, that interface was only added in version 1.6, so we have to add a
version check to keep things working with older sphinxes.

Signed-off-by: Jonathan Corbet <corbet@lwn.net>
Rebased for U-Boot
Signed-off-by: Heinrich Schuchardt <xypron.glpk@gmx.de>
diff --git a/doc/sphinx/kerneldoc.py b/doc/sphinx/kerneldoc.py
index fbedcc3..e536360 100644
--- a/doc/sphinx/kerneldoc.py
+++ b/doc/sphinx/kerneldoc.py
@@ -39,6 +39,8 @@
 from docutils.parsers.rst import directives, Directive
 from sphinx.ext.autodoc import AutodocReporter
 
+import kernellog
+
 __version__  = '1.0'
 
 class KernelDocDirective(Directive):
@@ -86,7 +88,8 @@
         cmd += [filename]
 
         try:
-            env.app.verbose('calling kernel-doc \'%s\'' % (" ".join(cmd)))
+            kernellog.verbose(env.app,
+                              'calling kernel-doc \'%s\'' % (" ".join(cmd)))
 
             p = subprocess.Popen(cmd, stdout=subprocess.PIPE, stderr=subprocess.PIPE)
             out, err = p.communicate()
@@ -96,7 +99,8 @@
             if p.returncode != 0:
                 sys.stderr.write(err)
 
-                env.app.warn('kernel-doc \'%s\' failed with return code %d' % (" ".join(cmd), p.returncode))
+                kernellog.warn(env.app,
+                               'kernel-doc \'%s\' failed with return code %d' % (" ".join(cmd), p.returncode))
                 return [nodes.error(None, nodes.paragraph(text = "kernel-doc missing"))]
             elif env.config.kerneldoc_verbosity > 0:
                 sys.stderr.write(err)
@@ -128,8 +132,8 @@
             return node.children
 
         except Exception as e:  # pylint: disable=W0703
-            env.app.warn('kernel-doc \'%s\' processing failed with: %s' %
-                         (" ".join(cmd), str(e)))
+            kernellog.warn(env.app, 'kernel-doc \'%s\' processing failed with: %s' %
+                           (" ".join(cmd), str(e)))
             return [nodes.error(None, nodes.paragraph(text = "kernel-doc missing"))]
 
 def setup(app):