Works without X11 by detecting missing X11 safely and switching to a non-X11...

Works without X11 by detecting missing X11 safely and switching to a non-X11 dependent backend if needed.

2b5d5c96d69a: without X use Agg backend for matplotlib.
0f9bc0082666: FIX: carbontracker did not accept Agg backend. Set backend before doing any other initialization.
a39f395df80b: Finally catch X11 errors the hard way: spawning a new process which tries to use X11. If that fails, use Agg as backend.

refactored/da/ct/tools.py

@@ -96,8 +96,3 @@ if __name__ == "__main__":
 
 
     show()
-
-    
-
-
-

refactored/da/tools/general.py

@@ -120,6 +120,7 @@ def ToDectime(dd):
     """ convert a datetime object to a decimal date """
     import datetime
     import calendar
+
     from matplotlib.pylab import date2num
 
     Days0=date2num(datetime.datetime(dd.year,1,1))

refactored/das.py

@@ -4,6 +4,19 @@
 # First order of business is always to make all other python modules accessible through the path
 #################################################################################################
 
+__realimport__ = __import__
+def _printimport(*args, **kwds):
+    """print each import."""
+    print "importing:", args[:1]
+    if args[0] == "matplotlib":
+        print args, kwds
+        raise Exception("Imported matplotlib here!")
+    return __realimport__(*args, **kwds)
+
+# debugging info to get the actual import order.
+#import __builtin__
+#__builtin__.__import__ = _printimport
+
 import sys
 import os
 import logging
@@ -13,6 +26,14 @@ dummy = sys.path.append(os.getcwd())
 # Next, import the tools needed to initialize a data assimilation cycle
 #################################################################################################
 
+# without X11 use Agg as matplotlib backend.
+from subprocess import call
+def hasWorkingX11():
+    return not call(["python", "-c", "import pylab as pl; pl.ion(); pl.plot((0,0))"])
+if not "DISPLAY" in os.environ or not hasWorkingX11(): 
+    import matplotlib
+    matplotlib.use("Agg")
+
 from da.tools.initexit import StartLogger
 from da.tools.initexit import ValidateOptsArgs
 from da.tools.initexit import ParseOptions