diff --git a/python/catkin/environment_cache.py b/python/catkin/environment_cache.py
index ebe14328c..3defa5211 100755
--- a/python/catkin/environment_cache.py
+++ b/python/catkin/environment_cache.py
@@ -59,9 +59,7 @@ def generate_environment_script(env_script):
     # fetch environment after calling setup
     python_code = 'import os; print(dict(os.environ))'
     output = subprocess.check_output([env_script, sys.executable, '-c', python_code])
-    if hasattr(sys.stdout, 'encoding') and sys.stdout.encoding:
-        output = output.decode(sys.stdout.encoding)
-    env_after = ast.literal_eval(output)
+    env_after = ast.literal_eval(output.decode('utf8'))
 
     # calculate added and modified environment variables
     added = {}
diff --git a/python/catkin/tidy_xml.py b/python/catkin/tidy_xml.py
index 2b2524625..c35e841f1 100644
--- a/python/catkin/tidy_xml.py
+++ b/python/catkin/tidy_xml.py
@@ -83,5 +83,5 @@ def tidy_xml(filename):
         data = data[:match.start()] + '?' + data[match.end():]
 
     with open(filename, 'w') as fhand:
-        fhand.write(data.encode('utf-8'))
+        fhand.write(data)
     return True
diff --git a/test/unit_tests/test_environment_cache.py b/test/unit_tests/test_environment_cache.py
index 01c621916..dc27e5e91 100644
--- a/test/unit_tests/test_environment_cache.py
+++ b/test/unit_tests/test_environment_cache.py
@@ -65,7 +65,7 @@ def test_generate_environment_script(self):
             catkin.environment_cache.os.environ = fake_environ
             rootdir = tempfile.mkdtemp()
             env_file = os.path.join(rootdir, 'env.sh')
-            with open(env_file, 'ab') as fhand:
+            with open(env_file, 'a') as fhand:
                 fhand.write('''\
 #! /usr/bin/env sh
 export FOO=/foo:/bar
diff --git a/test/unit_tests/test_terminal_color.py b/test/unit_tests/test_terminal_color.py
index d3f36d2e8..e2afc5612 100644
--- a/test/unit_tests/test_terminal_color.py
+++ b/test/unit_tests/test_terminal_color.py
@@ -7,6 +7,11 @@
         'Please adjust your pythonpath before running this test: %s' % str(e)
     )
 
+try:
+    char = unichr
+except NameError:
+    char = chr
+
 
 class TerminalColorTest(unittest.TestCase):
 
@@ -18,7 +23,7 @@ def test_terminal_colors(self):
         test = sanitize(test)
         rslt = 'This has bad stuff @! @/ @_ @| OK!\033[0m'
         assert fmt(test) == rslt
-        test = u'\u2018@'
+        test = char(2018)
         test = sanitize(test)
-        rslt = u'\u2018@@'
+        rslt = char(2018)
         assert test == rslt
diff --git a/test/unit_tests/test_tidy_xml.py b/test/unit_tests/test_tidy_xml.py
index de91c5bac..1080fa5cc 100644
--- a/test/unit_tests/test_tidy_xml.py
+++ b/test/unit_tests/test_tidy_xml.py
@@ -9,11 +9,16 @@
     raise ImportError(
         'Please adjust your pythonpath before running this test: %s' % str(impe))
 
+try:
+    char = unichr
+except NameError:
+    char = chr
+
 
 class TidyXmlTest(unittest.TestCase):
 
     def test_safe_xml_regex(self):
-        for data in [u'\u0000', u'\u000e']:
+        for data in [char(0), char(14)]:
             self.assertIsNotNone(_SAFE_XML_REGEX.match(data))
 
     def test_tiny_xml(self):
@@ -24,7 +29,7 @@ def test_tiny_xml(self):
 
             utf8_file = os.path.join(rootdir, 'utf8.xml')
             with open(utf8_file, 'ab') as fhand:
-                fhand.write(u'\u0000')
+                fhand.write(char(0).encode('utf8)'))
             tidy_xml(utf8_file)
             with open(utf8_file, 'r') as fhand:
                 contents = fhand.read()
@@ -32,7 +37,7 @@ def test_tiny_xml(self):
 
             iso_file = os.path.join(rootdir, 'iso.xml')
             with open(iso_file, 'ab') as fhand:
-                fhand.write(u'\u0000')
+                fhand.write(char(0).encode('ascii'))
             tidy_xml(iso_file)
             with open(iso_file, 'r') as fhand:
                 contents = fhand.read()