Fix behavior on PyPy3

.travis.yml

@@ -26,6 +26,9 @@ jobs:
     - python: "3.4"
     - python: "3.5"
     - python: "3.6"
+    - python: "3.7"
+      dist: xenial
+    - python: "pypy3"
 
     - stage: linting
       python: "3.6"

CHANGELOG.md

@@ -5,6 +5,7 @@
 ### Fixed
 
 - Fixed copy of TOML documents.
+- Fixed behavior on PyPy3.
 
 
 ## [0.5.2] - 2018-11-09

tomlkit/items.py

@@ -529,7 +529,10 @@ def __add__(self, other):
     def __sub__(self, other):
         result = super(DateTime, self).__sub__(other)
 
-        return self._new(result)
+        if isinstance(result, datetime):
+            result = self._new(result)
+
+        return result
 
     def _new(self, result):
         raw = result.isoformat()

tomlkit/source.py

@@ -47,10 +47,6 @@ def __exit__(self, exception_type, exception_val, trace):
             if self._save_marker:
                 self._source._marker = self._marker
 
-            # Restore exceptions are silently consumed, other exceptions need to
-            # propagate
-            return exception_type is None
-
 
 class _StateHandler:
     """

tox.ini

@@ -1,6 +1,6 @@
 [tox]
 isolated_build=true
-envlist = py27, py34, py35, py36, py37
+envlist = py27, py34, py35, py36, py37, pypy3
 
 [testenv]
 whitelist_externals = poetry