How to use the distlib.DistlibException function in distlib

"""
        Verify a signature for a file.

        :param signature_filename: The pathname to the file containing the
                                   signature.
        :param data_filename: The pathname to the file containing the
                              signed data.
        :return: True if the signature was verified, else False.
        """
        if not self.gpg:
            raise DistlibException('verification unavailable because gpg '
                                   'unavailable')
        cmd = self.get_verify_command(signature_filename, data_filename)
        rc, stdout, stderr = self.run_command(cmd)
        if rc not in (0, 1):
            raise DistlibException('verify command failed with error '
                             'code %s' % rc)
        return rc == 0

def sign_file(self, filename, signer, sign_password):
        """
        Sign a file.

        :param filename: The pathname to the file to be signed.
        :param signer: The identifier of the signer of the file.
        :param sign_password: The passphrase for the signer's
                              private key used for signing.
        :return: The absolute pathname of the file where the signature is
                 stored.
        """
        cmd, sig_file = self.get_sign_command(filename, signer, sign_password)
        rc, stdout, stderr = self.run_command(cmd,
                                              sign_password.encode('utf-8'))
        if rc != 0:
            raise DistlibException('sign command failed with error '
                                   'code %s' % rc)
        return sig_file

:param metadata: A :class:`Metadata` instance defining at least a name
                         and version number for the documentation to be
                         uploaded.
        :param doc_dir: The pathname of the directory which contains the
                        documentation. This should be the directory that
                        contains the ``index.html`` for the documentation.
        :return: The HTTP response received from PyPI upon submission of the
                request.
        """
        self.check_credentials()
        if not os.path.isdir(doc_dir):
            raise DistlibException('not a directory: %r' % doc_dir)
        fn = os.path.join(doc_dir, 'index.html')
        if not os.path.exists(fn):
            raise DistlibException('not found: %r' % fn)
        metadata.validate()
        name, version = metadata.name, metadata.version
        zip_data = zip_dir(doc_dir).getvalue()
        fields = [(':action', 'doc_upload'),
                  ('name', name), ('version', version)]
        files = [('content', name, zip_data)]
        request = self.encode_request(fields, files)
        return self.send_request(request)

def verify_signature(self, signature_filename, data_filename):
        """
        Verify a signature for a file.

        :param signature_filename: The pathname to the file containing the
                                   signature.
        :param data_filename: The pathname to the file containing the
                              signed data.
        :return: True if the signature was verified, else False.
        """
        if not self.gpg:
            raise DistlibException('verification unavailable because gpg '
                                   'unavailable')
        cmd = self.get_verify_command(signature_filename, data_filename)
        rc, stdout, stderr = self.run_command(cmd)
        if rc not in (0, 1):
            raise DistlibException('verify command failed with error '
                             'code %s' % rc)
        return rc == 0

def check_credentials(self):
        """
        Check that ``username`` and ``password`` have been set, and raise an
        exception if not.
        """
        if self.username is None or self.password is None:
            raise DistlibException('username and password must be set')
        pm = HTTPPasswordMgr()
        _, netloc, _, _, _, _ = urlparse(self.url)
        pm.add_password(self.realm, netloc, self.username, self.password)
        self.password_handler = HTTPBasicAuthHandler(pm)

def __init__(self, url=None):
        """
        Initialise an instance.

        :param url: The URL of the index. If not specified, the URL for PyPI is
                    used.
        """
        self.url = url or DEFAULT_INDEX
        self.read_configuration()
        scheme, netloc, path, params, query, frag = urlparse(self.url)
        if params or query or frag or scheme not in ('http', 'https'):
            raise DistlibException('invalid repository: %s' % self.url)
        self.password_handler = None
        self.ssl_verifier = None
        self.gpg = None
        self.gpg_home = None
        with open(os.devnull, 'w') as sink:
            for s in ('gpg2', 'gpg'):
                try:
                    rc = subprocess.check_call([s, '--version'], stdout=sink,
                                               stderr=sink)
                    if rc == 0:
                        self.gpg = s
                        break
                except OSError:
                    pass

def sign_file(self, filename, signer, sign_password):
        """
        Sign a file.

        :param filename: The pathname to the file to be signed.
        :param signer: The identifier of the signer of the file.
        :param sign_password: The passphrase for the signer's
                              private key used for signing.
        :return: The absolute pathname of the file where the signature is
                 stored.
        """
        cmd, sig_file = self.get_sign_command(filename, signer, sign_password)
        rc, stdout, stderr = self.run_command(cmd,
                                              sign_password.encode('utf-8'))
        if rc != 0:
            raise DistlibException('sign command failed with error '
                                   'code %s' % rc)
        return sig_file

def check_credentials(self):
        """
        Check that ``username`` and ``password`` have been set, and raise an
        exception if not.
        """
        if self.username is None or self.password is None:
            raise DistlibException('username and password must be set')
        pm = HTTPPasswordMgr()
        _, netloc, _, _, _, _ = urlparse(self.url)
        pm.add_password(self.realm, netloc, self.username, self.password)
        self.password_handler = HTTPBasicAuthHandler(pm)

def check_credentials(self):
        """
        Check that ``username`` and ``password`` have been set, and raise an
        exception if not.
        """
        if self.username is None or self.password is None:
            raise DistlibException('username and password must be set')
        pm = HTTPPasswordMgr()
        _, netloc, _, _, _, _ = urlparse(self.url)
        pm.add_password(self.realm, netloc, self.username, self.password)
        self.password_handler = HTTPBasicAuthHandler(pm)

block = sfp.read(blocksize)
                    if not block:
                        break
                    read += len(block)
                    dfp.write(block)
                    if digester:
                        digester.update(block)
                    blocknum += 1
                    if reporthook:
                        reporthook(blocknum, blocksize, size)
            finally:
                sfp.close()

        # check that we got the whole file, if we can
        if size >= 0 and read < size:
            raise DistlibException(
                'retrieval incomplete: got only %d out of %d bytes'
                % (read, size))
        # if we have a digest, it must match.
        if digester:
            actual = digester.hexdigest()
            if digest != actual:
                raise DistlibException('%s digest mismatch for %s: expected '
                                       '%s, got %s' % (hasher, destfile,
                                                       digest, actual))
            logger.debug('Digest verified: %s', digest)