diff -up src/sage/arith/multi_modular.pyx.orig src/sage/arith/multi_modular.pyx
--- src/sage/arith/multi_modular.pyx.orig	2018-08-03 05:10:08.000000000 -0600
+++ src/sage/arith/multi_modular.pyx	2018-08-29 10:44:04.624424587 -0600
@@ -173,9 +173,9 @@ cdef class MultiModularBasis_base(object
             ArithmeticError: The inverse of 6 modulo 10 is not defined.
         """
         if l_bound < 2:
-            raise ValueError(f"minimum value for lower bound is 2, given: {l_bound}")
+            raise ValueError("minimum value for lower bound is 2, given: {l_bound}".format(l_bound=l_bound))
         if u_bound > MAX_MODULUS:
-            raise ValueError(f"upper bound cannot be greater than {MAX_MODULUS}, given: {u_bound}")
+            raise ValueError("upper bound cannot be greater than {MAX_MODULUS}, given: {u_bound}".format(MAX_MODULUS=MAX_MODULUS, u_bound=u_bound))
 
         self._l_bound = l_bound
         self._u_bound = u_bound
@@ -234,7 +234,7 @@ cdef class MultiModularBasis_base(object
         if check:
             for p in plist:
                 if p > MAX_MODULUS:
-                    raise OverflowError(f"given modulus {p} is larger than {MAX_MODULUS}")
+                    raise OverflowError("given modulus {p} is larger than {MAX_MODULUS}".format(p=p, MAX_MODULUS=MAX_MODULUS))
         self._realloc_to_new_count(self.n + len_plist)
 
         cdef Py_ssize_t i
diff -up src/sage/rings/finite_rings/integer_mod.pyx.orig src/sage/rings/finite_rings/integer_mod.pyx
--- src/sage/rings/finite_rings/integer_mod.pyx.orig	2018-08-03 05:10:09.000000000 -0600
+++ src/sage/rings/finite_rings/integer_mod.pyx	2018-08-29 10:44:04.624424587 -0600
@@ -468,7 +468,7 @@ cdef class IntegerMod_abstract(FiniteRin
         from .integer_mod_ring import IntegerModRing
         R = IntegerModRing(modulus)
         if (<Element>self)._parent._IntegerModRing_generic__order % R.order():
-            raise ArithmeticError(f"reduction modulo {modulus!r} not defined")
+            raise ArithmeticError("reduction modulo {modulus} not defined".format(modulus=repr(modulus)))
         return R(self)
 
     def is_nilpotent(self):
diff -up src/sage/structure/parent.pyx.orig src/sage/structure/parent.pyx
--- src/sage/structure/parent.pyx.orig	2018-08-03 05:10:09.000000000 -0600
+++ src/sage/structure/parent.pyx	2018-08-29 10:44:04.625424574 -0600
@@ -726,7 +726,7 @@ cdef class Parent(sage.structure.categor
     cdef int init_coerce(self, bint warn=True) except -1:
         if self._coerce_from_hash is None:
             if warn:
-                raise AssertionError(f"unexpected call of init_coerce() for {type(self)}")
+                raise AssertionError("unexpected call of init_coerce() for {typ}".format(typ=type(self)))
             self._initial_coerce_list = []
             self._initial_action_list = []
             self._initial_convert_list = []
diff -up src/sage/symbolic/ring.pyx.orig src/sage/symbolic/ring.pyx
--- src/sage/symbolic/ring.pyx.orig	2018-08-03 05:10:09.000000000 -0600
+++ src/sage/symbolic/ring.pyx	2018-08-29 10:44:04.625424574 -0600
@@ -378,7 +378,7 @@ cdef class SymbolicRing(CommutativeRing)
             from sage.misc.all import prod
             return prod([SR(p)**e for p,e in x], SR(x.unit()))
         else:
-            raise TypeError(f"unable to convert {x!r} to a symbolic expression")
+            raise TypeError("unable to convert {x} to a symbolic expression".format(x=repr(x)))
 
         return new_Expression_from_GEx(self, exp)