Eigenvalues: Unable to extract eigenpair from SLEPc eigenvalue solver.

[Mathieu Doe]

Dear community, 

I am trying to run the example: https://fenics-solid-tutorial.readthedocs.io/en/latest/EigenvalueProblem/EigenvalueProblem.html (full code at the bottom).

But I the following issue: 

Traceback (most recent call last):
  File "/Users/mac/PycharmProjects/fenics_legacy/main.py", line 83, in <module>
    r, c, rx, cx = eigensolver.get_eigenpair(i)
                   ^^^^^^^^^^^^^^^^^^^^^^^^^^^^
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-...@googlegroups.com
***
*** Remember to include the error message listed below and, if possible,
*** include a *minimal* running example to reproduce the error.
***
*** -------------------------------------------------------------------------
*** Error:   Unable to extract eigenpair from SLEPc eigenvalue solver.
*** Reason:  Requested eigenpair (1) has not been computed.
*** Where:   This error was encountered inside SLEPcEigenSolver.cpp.
*** Process: 0
***
*** DOLFIN version: 2019.1.0
*** Git changeset:  
*** -------------------------------------------------------------------------

I tried:
-  i=1 intead of 0
- V = fe.VectorFunctionSpace(mesh, "CG", 3)

Any idea how to solve it?

Regards