export_to_vtk fails with Dolfin 2017.1.0

[ahellander]

Traceback (most recent call last):
File "simple_diffusion.py", line 37, in
result.export_to_vtk("A", "output")
File "/home/ubuntu/pyurdme/pyurdme/pyurdme.py", line 1753, in export_to_vtk
fd = dolfin.File(os.path.join(folder_name, "trajectory.xdmf").encode('ascii', 'ignore'))
File "/usr/lib/python2.7/dist-packages/dolfin/cpp/io.py", line 551, in init
_io.File_swiginit(self, _io.new_File(*args))
RuntimeError:

*** -------------------------------------------------------------------------
*** DOLFIN encountered an error. If you are not able to resolve this issue
*** using the information listed below, you can ask for help at

---

*** fenics-support@googlegroups.com

---

*** Remember to include the error message listed below and, if possible,
*** include a minimal running example to reproduce the error.

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*** -------------------------------------------------------------------------
*** Error: Unable to open file.
*** Reason: Unknown file type (".xdmf") for file "output/trajectory.xdmf".
*** Where: This error was encountered inside File.cpp.
*** Process: 0

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*** DOLFIN version: 2017.1.0
*** Git changeset: unknown
*** -------------------------------------------------------------------------

[ahellander]

This is due to a docuemented change in the Dolfin interface, from ChangeLog:

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Remove XDMF from File interface. XDMF is XML based, and has many possibilities for file access, which are not accessible through the limited File interface and “<<” “>>” operators. Instead of File, use XDMFFile, and use XDMFFile.read() and XDMFFile.write() for I/O. Demos and tests have been updated to show usage. XDMF now also supports ASCII I/O in serial, useful for compatibility with users who do not have the HDF5 library available.