Py3: Fix matrix/docs.py doctests errors

[vklein]

Fix matrix/docs.py doctests errors. Example :

File "src/sage/matrix/docs.py", line 115, in sage.matrix.docs
Failed example:
    M[range(2),:]
Exception raised:
    Traceback (most recent call last):
      File "/home/u1/chapoton/sage3/local/lib/python3.6/site-packages/sage/doctest/forker.py", line 671, in _run
        self.compile_and_execute(example, compiler, test.globs)
      File "/home/u1/chapoton/sage3/local/lib/python3.6/site-packages/sage/doctest/forker.py", line 1095, in compile_and_execute
        exec(compiled, globs)
      File "<doctest sage.matrix.docs[14]>", line 1, in <module>
        M[range(Integer(2)),:]
      File "sage/matrix/matrix0.pyx", line 926, in sage.matrix.matrix0.Matrix.__getitem__ (build/cythonized/sage/matrix/matrix0.c:6734)
        raise TypeError("index must be an integer")
    TypeError: index must be an integer

These errors were caused by range calls (range return iterator in py3).

[chapoton]

possible conflict with #27585 ?

[vklein]

Replying to chapoton:

possible conflict with #27585 ?

It's ok #27585 doesn't modifiy matrix/docs.py

---

New commits:

​4d569a5

Trac 27586: Py3 Fix matrix/docs.py doctests

[jhpalmieri]

#27585 makes changes to allow M[range(2),:] to work with Python 3. In particular, it should fix the doctests you are changing. I would request that you put this on hold until #27585 is resolved.

[vklein]

My bad i have missed that point.