base: Add warn() and inform() to m5.utils for use from python

This patch adds two fuctions to m5.util, warn and inform, which mirror those
found in the C++ side of gem5. These are added in addition to the already
existing m5.util.panic and m5.util.fatal which already mirror the C++
functionality. This ensures that warning and information messages generated
by python are in the same format as those generated by C++.

Occurrences of
    print "Warning: %s..." % name
have been replaced with
    warn("%s...", name)

src/python/m5/util/__init__.py

@@ -56,6 +56,17 @@ def fatal(fmt, *args):
     print >>sys.stderr, 'fatal:', fmt % args
     sys.exit(1)
 
+# warn() should be called when the user should be warned about some condition
+# that may or may not be the user's fault, but that they should be made aware
+# of as it may affect the simulation or results.
+def warn(fmt, *args):
+    print >>sys.stderr, 'warn:', fmt % args
+
+# inform() should be called when the user should be informed about some
+# condition that they may be interested in.
+def inform(fmt, *args):
+    print >>sys.stdout, 'info:', fmt % args
+
 class Singleton(type):
     def __call__(cls, *args, **kwargs):
         if hasattr(cls, '_instance'):

src/python/m5/util/dot_writer.py

@@ -57,6 +57,7 @@
 
 import m5, os, re
 from m5.SimObject import isRoot, isSimObjectVector
+from m5.util import warn
 try:
     import pydot
 except:
@@ -176,4 +177,4 @@ def do_dot(root, outdir, dotFilename):
         # So avoid terminating simulation unnecessarily
         callgraph.write_pdf(dot_filename + ".pdf")
     except:
-        print "warning: failed to generate pdf output from %s" % dot_filename
+        warn("failed to generate pdf output from %s", dot_filename)