Matrix results with a single column come back as a vector (Inverse[{{2}}], RowReduce[{{1}, {2}}], ...) #2006

Matrix results that come back from SymPy with a single column are returned as a vector instead of an n×1 matrix:

In[1]:= Inverse[{{2}}]
Out[1]= {1/2}            (* WMA: {{1/2}} *)

In[2]:= RowReduce[{{1}, {2}}]
Out[2]= {1, 0}           (* WMA: {{1}, {0}} *)

In[3]:= MatrixPower[{{2}}, 3]
Out[3]= {8}              (* WMA: {{8}} *)

In[4]:= MatrixExp[{{0}}]
Out[4]= {1}              (* WMA: {{1}} *)

In[5]:= Transpose[{{1, 2, 3}}]
Out[5]= {1, 2, 3}        (* WMA: {{1}, {2}, {3}} *)

The cause is from_sympy_matrix in mathics/core/convert/sympy.py, which turns every matrix of shape (n, 1) into a list of its entries. That is what callers want when the matrix stands for a vector (e.g. a solution vector), but not when the result is itself a matrix. A fix probably needs the callers that want a vector to ask for it explicitly.

Found on master (4aa7411). Transpose alone is fixed in #2007, since it does not need SymPy at all.

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