def _get_version_from_pkg_metadata(package_name):
    """Get the version from package metadata if present.

    This looks for PKG-INFO if present (for sdists), and if not looks
    for METADATA (for wheels) and failing that will return None.
    """
    pkg_metadata_filenames = ['PKG-INFO', 'METADATA']
    pkg_metadata = {}
    for filename in pkg_metadata_filenames:
        try:
            pkg_metadata_file = open(filename, 'r')
        except (IOError, OSError):
            continue
        try:
            pkg_metadata = email.message_from_file(pkg_metadata_file)
        except email.errors.MessageError:
            continue

    # Check to make sure we're in our own dir
    if pkg_metadata.get('Name', None) != package_name:
        return None
    return pkg_metadata.get('Version', None) 

def _get_version_from_pkg_metadata(package_name):
    """Get the version from package metadata if present.

    This looks for PKG-INFO if present (for sdists), and if not looks
    for METADATA (for wheels) and failing that will return None.
    """
    pkg_metadata_filenames = ['PKG-INFO', 'METADATA']
    pkg_metadata = {}
    for filename in pkg_metadata_filenames:
        try:
            pkg_metadata_file = open(filename, 'r')
        except (IOError, OSError):
            continue
        try:
            pkg_metadata = email.message_from_file(pkg_metadata_file)
        except email.errors.MessageError:
            continue

    # Check to make sure we're in our own dir
    if pkg_metadata.get('Name', None) != package_name:
        return None
    return pkg_metadata.get('Version', None) 

def _http_request_requests(self, url, headers, data, params):
        kwargs = {
            'verify': self.verify_cert,
        }
        if url is not None:
            kwargs['url'] = url
        if headers is not None:
            kwargs['headers'] = headers
        if data is not None:
            kwargs['data'] = data
        if params is not None:
            kwargs['params'] = params
        if self.timeout is not None:
            kwargs['timeout'] = self.timeout

        try:
            if data is None:
                r = requests.get(**kwargs)
            else:
                r = requests.post(**kwargs)
        except requests.exceptions.RequestException as e:
            raise PanHttpError('RequestException: ' + str(e))

        self.code = r.status_code
        self.reason = r.reason
        x = ['%s: %s' % (k, v) for k, v in r.headers.items()]
        try:
            self.headers = email.message_from_string('\n'.join(x))
        except (TypeError, email.errors.MessageError) as e:
            raise PanHttpError('email.message_from_string() %s' % e)
        self.encoding = self.headers.get_content_charset('utf8')
        self.content_type = self.headers.get_content_type()
        self.content = r.content
        self.text = r.text

    # allow non-2XX error codes
    # see http://bugs.python.org/issue18543 for why we can't just
    # install a new HTTPErrorProcessor() 

def test_email_parsing_errors_are_handled(self):
        mocked_open = mock.mock_open()
        with mock.patch('pbr.packaging.open', mocked_open):
            with mock.patch('email.message_from_file') as message_from_file:
                message_from_file.side_effect = [
                    email.errors.MessageError('Test'),
                    {'Name': 'pbr_testpackage'}]
                version = packaging._get_version_from_pkg_metadata(
                    'pbr_testpackage')

        self.assertTrue(message_from_file.called)
        self.assertIsNone(version) 

def get_text_content(msg, errors='replace'):
    content = msg.get_payload(decode=True)
    charset = msg.get_param('charset', 'ASCII')
    return content.decode(charset, errors=errors) 

def _prepare_set(msg, maintype, subtype, headers):
    msg['Content-Type'] = '/'.join((maintype, subtype))
    if headers:
        if not hasattr(headers[0], 'name'):
            mp = msg.policy
            headers = [mp.header_factory(*mp.header_source_parse([header]))
                       for header in headers]
        try:
            for header in headers:
                if header.defects:
                    raise header.defects[0]
                msg[header.name] = header
        except email.errors.HeaderDefect as exc:
            raise ValueError("Invalid header: {}".format(
                                header.fold(policy=msg.policy))) from exc 

def get_text_content(msg, errors='replace'):
    content = msg.get_payload(decode=True)
    charset = msg.get_param('charset', 'ASCII')
    return content.decode(charset, errors=errors) 

def _prepare_set(msg, maintype, subtype, headers):
    msg['Content-Type'] = '/'.join((maintype, subtype))
    if headers:
        if not hasattr(headers[0], 'name'):
            mp = msg.policy
            headers = [mp.header_factory(*mp.header_source_parse([header]))
                       for header in headers]
        try:
            for header in headers:
                if header.defects:
                    raise header.defects[0]
                msg[header.name] = header
        except email.errors.HeaderDefect as exc:
            raise ValueError("Invalid header: {}".format(
                                header.fold(policy=msg.policy))) from exc 

def get_text_content(msg, errors='replace'):
    content = msg.get_payload(decode=True)
    charset = msg.get_param('charset', 'ASCII')
    return content.decode(charset, errors=errors) 

def _prepare_set(msg, maintype, subtype, headers):
    msg['Content-Type'] = '/'.join((maintype, subtype))
    if headers:
        if not hasattr(headers[0], 'name'):
            mp = msg.policy
            headers = [mp.header_factory(*mp.header_source_parse([header]))
                       for header in headers]
        try:
            for header in headers:
                if header.defects:
                    raise header.defects[0]
                msg[header.name] = header
        except email.errors.HeaderDefect as exc:
            raise ValueError("Invalid header: {}".format(
                                header.fold(policy=msg.policy))) from exc 

def get_text_content(msg, errors='replace'):
    content = msg.get_payload(decode=True)
    charset = msg.get_param('charset', 'ASCII')
    return content.decode(charset, errors=errors) 

def _prepare_set(msg, maintype, subtype, headers):
    msg['Content-Type'] = '/'.join((maintype, subtype))
    if headers:
        if not hasattr(headers[0], 'name'):
            mp = msg.policy
            headers = [mp.header_factory(*mp.header_source_parse([header]))
                       for header in headers]
        try:
            for header in headers:
                if header.defects:
                    raise header.defects[0]
                msg[header.name] = header
        except email.errors.HeaderDefect as exc:
            raise ValueError("Invalid header: {}".format(
                                header.fold(policy=msg.policy))) from exc 

def _iter_parts(msg):
        """Extract and decode the text parts from the parsed email message.
        For non-text parts the payload will be None.

        Yields (payload, part)
        """
        for part in msg.walk():
            if part.get_content_maintype() == "text":
                payload = part.get_payload(decode=True)

                charset = part.get_content_charset()
                errors = "ignore"
                if not charset:
                    charset = "ascii"
                elif charset.lower().replace("_", "-") in STRICT_CHARSETS:
                    errors = "strict"
                try:
                    payload = payload.decode(charset, errors)
                except (LookupError, UnicodeError, AssertionError):
                    try:
                        payload = payload.decode("ascii", "ignore")
                    except UnicodeError:
                        continue
                yield payload, part
            else:
                yield None, part 

def get_text_content(msg, errors='replace'):
    content = msg.get_payload(decode=True)
    charset = msg.get_param('charset', 'ASCII')
    return content.decode(charset, errors=errors) 

def _prepare_set(msg, maintype, subtype, headers):
    msg['Content-Type'] = '/'.join((maintype, subtype))
    if headers:
        if not hasattr(headers[0], 'name'):
            mp = msg.policy
            headers = [mp.header_factory(*mp.header_source_parse([header]))
                       for header in headers]
        try:
            for header in headers:
                if header.defects:
                    raise header.defects[0]
                msg[header.name] = header
        except email.errors.HeaderDefect as exc:
            raise ValueError("Invalid header: {}".format(
                                header.fold(policy=msg.policy))) from exc 

def get_text_content(msg, errors='replace'):
    content = msg.get_payload(decode=True)
    charset = msg.get_param('charset', 'ASCII')
    return content.decode(charset, errors=errors) 

def _prepare_set(msg, maintype, subtype, headers):
    msg['Content-Type'] = '/'.join((maintype, subtype))
    if headers:
        if not hasattr(headers[0], 'name'):
            mp = msg.policy
            headers = [mp.header_factory(*mp.header_source_parse([header]))
                       for header in headers]
        try:
            for header in headers:
                if header.defects:
                    raise header.defects[0]
                msg[header.name] = header
        except email.errors.HeaderDefect as exc:
            raise ValueError("Invalid header: {}".format(
                                header.fold(policy=msg.policy))) from exc 

def get_text_content(msg, errors='replace'):
    content = msg.get_payload(decode=True)
    charset = msg.get_param('charset', 'ASCII')
    return content.decode(charset, errors=errors) 

def _prepare_set(msg, maintype, subtype, headers):
    msg['Content-Type'] = '/'.join((maintype, subtype))
    if headers:
        if not hasattr(headers[0], 'name'):
            mp = msg.policy
            headers = [mp.header_factory(*mp.header_source_parse([header]))
                       for header in headers]
        try:
            for header in headers:
                if header.defects:
                    raise header.defects[0]
                msg[header.name] = header
        except email.errors.HeaderDefect as exc:
            raise ValueError("Invalid header: {}".format(
                                header.fold(policy=msg.policy))) from exc 

def test_email_parsing_errors_are_handled(self):
        mocked_open = mock.mock_open()
        with mock.patch('pbr.packaging.open', mocked_open):
            with mock.patch('email.message_from_file') as message_from_file:
                message_from_file.side_effect = [
                    email.errors.MessageError('Test'),
                    {'Name': 'pbr_testpackage'}]
                version = packaging._get_version_from_pkg_metadata(
                    'pbr_testpackage')

        self.assertTrue(message_from_file.called)
        self.assertIsNone(version) 

def _http_request_urllib(self, url, headers, data, params):
        if params is not None:
            url += '?' + urlencode(params)

        kwargs = {}
        if url is not None:
            kwargs['url'] = url
        if headers is not None:
            kwargs['headers'] = headers
        if data is not None:
            kwargs['data'] = data
            if headers is not None:
                x = set(k.lower() for k in headers)
                if not 'content-type' in x:
                    kwargs['data'] = urlencode(data)
            # data must by type 'bytes' for 3.x
            if _isunicode(kwargs['data']):
                kwargs['data'] = kwargs['data'].encode()

        request = Request(**kwargs)

        kwargs = {
            'url': request,
        }
        if self.timeout is not None:
            kwargs['timeout'] = self.timeout

        if not self.verify_cert and \
            (sys.version_info.major == 2 and
             sys.hexversion >= 0x02070900 or
             sys.version_info.major == 3 and
             sys.hexversion >= 0x03040300):
            context = ssl._create_unverified_context()
            kwargs['context'] = context

        try:
            response = self._urlopen(**kwargs)
        except (URLError, IOError, ssl.CertificateError) as e:
            # IOError for urllib timeouts
            # ssl.CertificateError for mismatching hostname
            raise PanHttpError(str(e))

        self.code = response.getcode()
        if hasattr(response, 'reason'):
            # 3.2
            self.reason = response.reason
        elif hasattr(response, 'msg'):
            # 2.7
            self.reason = response.msg

        try:
            self.headers = email.message_from_string(str(response.info()))
        except (TypeError, email.errors.MessageError) as e:
            raise PanHttpError('email.message_from_string() %s' % e)

        self.encoding = self.headers.get_content_charset('utf8')
        self.content_type = self.headers.get_content_type()
        self.content = response.read()
        self.text = self.content.decode(self.encoding)