Add encoding declaration to test_sympy_parser
Add encoding declaration to test_sympy_parser

Part of #15503. The test_sympy_parser module has includes non-ASCII
characters. This is not importable on Py2 without an encoding
declaration. This error does not show up using bin/test because bin/test
uses compile/exec rather than importing the module normally.

kaushik94/sympy,kaushik94/sympy,kaushik94/sympy