catch scipy 0.9 bug in tutorial example

doc/source/tutorial/closed_system.py

@@ -99,14 +99,22 @@ def main():
     # Finalize the system.
     sys = sys.finalized()
 
-    # We should observe energy levels that flow towards Landau
-    # level energies with increasing magnetic field
-    plot_spectrum(sys, [iB * 0.002 for iB in xrange(100)])
-
-    # Plot an eigenmode of a circular dot. Here we create a larger system for
-    # better spatial resolution.
-    sys = make_system(r=30).finalized()
-    plot_wave_function(sys)
+    # The following try-clause can be removed once SciPy 0.9 becomes uncommon.
+    try:
+        # We should observe energy levels that flow towards Landau
+        # level energies with increasing magnetic field.
+        plot_spectrum(sys, [iB * 0.002 for iB in xrange(100)])
+
+        # Plot an eigenmode of a circular dot. Here we create a larger system for
+        # better spatial resolution.
+        sys = make_system(r=30).finalized()
+        plot_wave_function(sys)
+    except ValueError as e:
+        if e.message == "Input matrix is not real-valued.":
+            print "The calculation of eigenvalues failed because of a bug in SciPy 0.9."
+            print "Please upgrade to a newer version of SciPy."
+        else:
+            raise
 
 
 # Call the main function if the script gets executed (as opposed to imported).