Error with Solve() on Mac OS X 10.11.6

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Hello,

Downloaded Sage 7.3 (the ...64.app.dmg download) for the first time and learning the interface. I tried to solve a nonlinear equation of some complexity and got an error. I followed up with the following example from the Sage 7.3 tutorial manual:

g = var('g')
solve(g^2 + 3*g + 2, g)

and received this error (the same error as the equation of some complexity)

Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "_sage_input_60.py", line 10, in <module>
    exec compile(u'open("___code___.py","w").write("# -*- coding: utf-8 -*-\\n" + _support_.preparse_worksheet_cell(base64.b64decode("WF9BID0gdmFyKCdYX0EnKQpERVEgPSAoRl9hMCkqKFhfQSkgPT0gVl9jCnNvbHZlKFtERVFdLCBYX0Ep"),globals())+"\\n"); execfile(os.path.abspath("___code___.py"))
  File "", line 1, in <module>

  File "/private/var/folders/61/8zfqb4g12xl87lp5x2sk4g_r0000gn/T/tmpQtR_UQ/___code___.py", line 4, in <module>
    exec compile(u'solve([DEQ], X_A)
  File "", line 1, in <module>

  File "/Applications/SageMath-7.3.app/Contents/Resources/sage/local/lib/python2.7/site-packages/sage/symbolic/relation.py", line 810, in solve
    return f[0].solve(*args,**kwds)
  File "sage/symbolic/expression.pyx", line 10679, in sage.symbolic.expression.Expression.solve (/Applications/SageMath-7.3.app/Contents/Resources/sage/src/build/cythonized/sage/symbolic/expression.cpp:53735)
  File "sage/symbolic/expression.pyx", line 802, in sage.symbolic.expression.Expression._maxima_ (/Applications/SageMath-7.3.app/Contents/Resources/sage/src/build/cythonized/sage/symbolic/expression.cpp:7281)
  File "sage/structure/sage_object.pyx", line 673, in sage.structure.sage_object.SageObject._interface_ (/Applications/SageMath-7.3.app/Contents/Resources/sage/src/build/cythonized/sage/structure/sage_object.c:5506)
  File "sage/misc/lazy_import.pyx", line 354, in sage.misc.lazy_import.LazyImport.__getattr__ (/Applications/SageMath-7.3.app/Contents/Resources/sage/src/build/cythonized/sage/misc/lazy_import.c:3486)
  File "sage/misc/lazy_import.pyx", line 246, in sage.misc.lazy_import.LazyImport._get_object (/Applications/SageMath-7.3.app/Contents/Resources/sage/src/build/cythonized/sage/misc/lazy_import.c:2241)
  File "/Applications/SageMath-7.3.app/Contents/Resources/sage/local/lib/python2.7/site-packages/sage/interfaces/maxima_lib.py", line 105, in <module>
    ecl_eval("(set-locale-subdir)")
  File "sage/libs/ecl.pyx", line 1315, in sage.libs.ecl.ecl_eval (/Applications/SageMath-7.3.app/Contents/Resources/sage/src/build/cythonized/sage/libs/ecl.c:10158)
  File "sage/libs/ecl.pyx", line 1330, in sage.libs.ecl.ecl_eval (/Applications/SageMath-7.3.app/Contents/Resources/sage/src/build/cythonized/sage/libs/ecl.c:10097)
  File "sage/libs/ecl.pyx", line 343, in sage.libs.ecl.ecl_safe_eval (/Applications/SageMath-7.3.app/Contents/Resources/sage/src/build/cythonized/sage/libs/ecl.c:5162)
RuntimeError: ECL says: The function SET-LOCALE-SUBDIR is undefined.

Didn't get much luck with google searches on the exact cause of this, but some sources recommended installing Xcode or iPython, though I do not have any rational to connect the reccomended solution to the original problem.

Update:

I downloaded Xcode 7.3.1 and Command Tools per the instructions,(Command_Line_Tools_OS_X_10.11_for_Xcode_7.3.1).

First I downloaded Command Tools only, and tried Sage, and the result below occurred. Next I downloaded Xcode and initialized Xcode, it did not work ... (more)