Fix error in approx's repr with complex numbers

Fix #2082

CHANGELOG.rst

@@ -7,6 +7,10 @@
   subtle bugs (`#2078`_).
   Thanks `@nicoddemus`_ for the PR.
 
+* Fix error message using ``approx`` with complex numbers (`#2082`_).
+  Thanks `@adler-j`_ for the report and `@nicoddemus`_ for the PR.
+
+*
 
 * Cope gracefully with a .pyc file with no matching .py file (`#2038`_). Thanks
   `@nedbat`_.
@@ -15,10 +19,12 @@
 
 *
 
+.. _@adler-j: https://github.com/adler-j
 .. _@nedbat: https://github.com/nedbat
 
 .. _#2038: https://github.com/pytest-dev/pytest/issues/2038
 .. _#2078: https://github.com/pytest-dev/pytest/issues/2078
+.. _#2082: https://github.com/pytest-dev/pytest/issues/2082
 
 
 3.0.4

_pytest/python.py

@@ -1419,6 +1419,9 @@ class ApproxNonIterable(object):
         self.rel = rel
 
     def __repr__(self):
+        if isinstance(self.expected, complex):
+            return str(self.expected)
+
         # Infinities aren't compared using tolerances, so don't show a
         # tolerance.
         if math.isinf(self.expected):

testing/python/approx.py

@@ -28,6 +28,7 @@ class TestApprox:
         print(approx(inf))
         print(approx(1.0, rel=nan))
         print(approx(1.0, rel=inf))
+        print(approx(1.0j, rel=inf))
 
     def test_operator_overloading(self):
         assert 1 == approx(1, rel=1e-6, abs=1e-12)