Make dependency on cchardet optional

Ported from #84

.travis.yml

@@ -3,7 +3,7 @@ python:
   - 2.7
   - 3.6
 install:
-  - pip install -e .[validator]
+  - pip install -e .[cchardet,validator]
   - pip install nose mock coverage coveralls
 script: ./build.sh
 after_success:

CHANGELOG.md

@@ -0,0 +1,20 @@
+# Changelog
+All notable changes to this project will be documented in this file.
+
+The format is based on [Keep a Changelog](http://keepachangelog.com/en/1.0.0/)
+and this project adheres to [Semantic Versioning](http://semver.org/spec/v2.0.0.html).
+
+## [Unreleased]
+- Dependency on cchardet was made optional. Ported from [PR84](https://github.com/mailgun/flanker/pull/84)
+
+## [0.8.5] - 2018-03-30
+### Changed
+- MAX_HEADER_LENGTH (8000) and MAX_LINE_LENGTH (10000) parser limits were
+ removed. 
+- A bunch of implementation details were "hidden" in underscore prefixed
+ files/folders. This change is technically breaking, but those files were
+ never supposed to be used directly. 
+
+## [0.8.4] - 2018-02-01
+The change log has not been kept up to release v0.8.5. The only reliable
+ source of information is the commit log on [GitHub](https://github.com/mailgun/flanker/commits/master).

flanker/mime/message/utils.py

@@ -1,21 +1,29 @@
 from contextlib import closing
 from email.generator import Generator
 
-import cchardet
-import chardet
+import chardet as fallback_detector
 import six
 
+# Made cchardet optional according to https://github.com/mailgun/flanker/pull/84
+try:
+    import cchardet as primary_detector
+except ImportError:
+    primary_detector = fallback_detector
+
 from flanker.mime.message import errors
 
 
 def python_message_to_string(msg):
-    """Converts python message to string in a proper way"""
+    """
+    Converts python message to string in a proper way.
+    """
     with closing(six.StringIO()) as fp:
         g = Generator(fp, mangle_from_=False)
         g.flatten(msg, unixfrom=False)
         return fp.getvalue()
 
-def _guess_and_convert_with(value, detector=cchardet):
+
+def _guess_and_convert_with(value, detector=primary_detector):
     """
     Try to guess the encoding of the passed value with the provided detector
     and decode it.
@@ -34,6 +42,7 @@ def _guess_and_convert_with(value, detector=cchardet):
     except (UnicodeError, LookupError) as e:
         raise errors.DecodingError(str(e))
 
+
 def _guess_and_convert(value):
     """
     Try to guess the encoding of the passed value and decode it.
@@ -42,9 +51,9 @@ def _guess_and_convert(value):
     back to chardet which is much slower.
     """
     try:
-        return _guess_and_convert_with(value, detector=cchardet)
-    except:
-        return _guess_and_convert_with(value, detector=chardet)
+        return _guess_and_convert_with(value, detector=primary_detector)
+    except Exception:
+        return _guess_and_convert_with(value, detector=fallback_detector)
 
 
 def _make_unicode(value, charset=None):
@@ -61,12 +70,9 @@ def _make_unicode(value, charset=None):
 
 
 def to_utf8(value, charset=None):
-    '''
+    """
     Safely returns a UTF-8 version of a given string
-    >>> utils.to_utf8(u'hi')
-        'hi'
-    '''
-
+    """
     value = _make_unicode(value, charset)
 
     return value.encode("utf-8", "strict")

setup.py

@@ -22,7 +22,6 @@
       install_requires=[
           'attrs',
           'chardet>=1.0.1',
-          'cchardet>=0.3.5',
           'cryptography>=0.5',
           'idna>=2.5',
           'ply>=3.10',
@@ -35,4 +34,7 @@
               'dnsq>=1.1.6',
               'redis>=2.7.1',
           ],
+          'cchardet': [
+              'cchardet>=0.3.5',
+          ]
       })