Use more @contract, less assert

2 files changed, 2 insertions, 3 deletions

diff --git a/coverage/phystokens.py b/coverage/phystokens.py
index 587ec1c6..1bc6330d 100644
--- a/coverage/phystokens.py
+++ b/coverage/phystokens.py
@@ -151,6 +151,7 @@ generate_tokens = CachedTokenizer().generate_tokens
 
 COOKIE_RE = re.compile(r"^\s*#.*coding[:=]\s*([-\w.]+)", flags=re.MULTILINE)
 
+@contract(source='bytes')
 def _source_encoding_py2(source):
     """Determine the encoding for `source`, according to PEP 263.
 
@@ -247,6 +248,7 @@ def _source_encoding_py2(source):
     return default
 
 
+@contract(source='bytes')
 def _source_encoding_py3(source):
     """Determine the encoding for `source`, according to PEP 263.
 
@@ -257,7 +259,6 @@ def _source_encoding_py3(source):
         string: the name of the encoding.
 
     """
-    assert isinstance(source, bytes)
     readline = iternext(source.splitlines(True))
     return tokenize.detect_encoding(readline)[0]
 
diff --git a/coverage/python.py b/coverage/python.py
index 3e8e9f39..faa26ffc 100644
--- a/coverage/python.py
+++ b/coverage/python.py
@@ -77,7 +77,6 @@ def get_zip_bytes(filename):
                 data = zi.get_data(parts[1])
             except IOError:
                 continue
-            assert isinstance(data, bytes)
             return data
     return None
 
@@ -160,7 +159,6 @@ class PythonFileReporter(FileReporter):
     def source(self):
         if self._source is None:
             self._source = get_python_source(self.filename)
-            assert isinstance(self._source, unicode_class)
         return self._source
 
     def should_be_python(self):