src/sage/rings/rational.pyx: Move import of mathml into method

Author: Matthias Koeppe

src/sage/rings/rational.pyx

@@ -65,7 +65,6 @@ from cysignals.signals cimport sig_on, sig_off
 import operator
 import fractions
 
-from sage.misc.mathml import mathml
 from sage.arith.long cimport pyobject_to_long, integer_check_long_py
 from sage.cpython.string cimport char_to_str, str_to_bytes
 
@@ -1082,6 +1081,7 @@ cdef class Rational(sage.structure.element.FieldElement):
         if self.denom() == 1:
             return '<mn>%s</mn>'%(self.numer())
         else:
+            from sage.misc.mathml import mathml
             t = ''
             if self < 0:
                 t = t + '<mo>-</mo>'