Fix mathtext mismatched braces

Author: devRD

lib/matplotlib/_mathtext.py

@@ -2030,7 +2030,8 @@ def main(self, s, loc, toks):
         return [Hlist(toks)]
 
     def math_string(self, s, loc, toks):
-        return self._math_expression.parseString(toks[0][1:-1])
+        return self._math_expression.parseString(toks[0][1:-1],
+                                                 parseAll=True)
 
     def math(self, s, loc, toks):
         hlist = Hlist(toks)

lib/matplotlib/tests/test_mathtext.py

@@ -320,6 +320,7 @@ def test_fontinfo():
         (r'$a^2^2$', r'Double superscript'),
         (r'$a_2_2$', r'Double subscript'),
         (r'$a^2_a^2$', r'Double superscript'),
+        (r'$a = {b$', r'Expected end of text'),
     ],
     ids=[
         'hspace without value',
@@ -347,7 +348,8 @@ def test_fontinfo():
         'unknown symbol',
         'double superscript',
         'double subscript',
-        'super on sub without braces'
+        'super on sub without braces',
+        'math string with no closing braces'
     ]
 )
 def test_mathtext_exceptions(math, msg):