This fix for Python 3.8 warnings is already applied in upstream and
should probably be removed after next mpmath release.

diff --git a/mpmath/ctx_mp_python.py b/mpmath/ctx_mp_python.py
--- a/mpmath/ctx_mp_python.py
+++ b/mpmath/ctx_mp_python.py
@@ -889,7 +889,7 @@ def fsum(ctx, terms, absolute=False, squared=False):
             s = ctx.make_mpc((s, mpf_sum(imag, prec, rnd)))
         else:
             s = ctx.make_mpf(s)
-        if other is 0:
+        if other == 0:
             return s
         else:
             return s + other
@@ -983,7 +983,7 @@ def fdot(ctx, A, B=None, conjugate=False):
             s = ctx.make_mpc((s, mpf_sum(imag, prec, rnd)))
         else:
             s = ctx.make_mpf(s)
-        if other is 0:
+        if other == 0:
             return s
         else:
             return s + other