import json


class JIRAError(Exception):
    """General error raised for all problems in operation of the client."""
    def __init__(self, status_code=None, text=None, url=None):
        self.status_code = status_code
        self.text = text
        self.url = url

    def __str__(self):
        if self.text:
            return 'HTTP {0}: "{1}"\n{2}'.format(self.status_code, self.text, self.url)
        else:
            return 'HTTP {0}: {1}'.format(self.status_code, self.url)


def raise_on_error(r):
    if r.status_code >= 400:
        error = ''
        if r.text:
            try:
                response = json.loads(r.text)
                if 'message' in response:
                    # JIRA 5.1 errors
                    error = response['message']
                elif 'errorMessages' in response:
                    # JIRA 5.0.x error messages sometimes come wrapped in this array
                    errorMessages = response['errorMessages']
                    if isinstance(errorMessages, (list, tuple)) and len(errorMessages) > 0:
                        error = errorMessages[0]
                    else:
                        error = errorMessages
                else:
                    error = r.text
            except ValueError:
                error = r.text
        raise JIRAError(r.status_code, error, r.url)

import json


class JIRAError(Exception):
    """General error raised for all problems in operation of the client."""
    def __init__(self, status_code=None, text=None, url=None):
        self.status_code = status_code
        self.text = text
        self.url = url

    def __str__(self):
        if self.text:
            return 'HTTP {0}: "{1}"\n{2}'.format(self.status_code, self.text, self.url)
        else:
            return 'HTTP {0}: {1}'.format(self.status_code, self.url)


def raise_on_error(r):
    if r.status_code >= 400:
        error = ''
        if r.text:
            try:
                response = json.loads(r.text)
                if 'message' in response:
                    # JIRA 5.1 errors
                    error = response['message']
                elif 'errorMessages' in response and len(response['errorMessages']) > 0:
                    # JIRA 5.0.x error messages sometimes come wrapped in this array
                    # Sometimes this is present but empty
                    errorMessages = response['errorMessages']
                    if isinstance(errorMessages, (list, tuple)):
                        error = errorMessages[0]
                    else:
                        error = errorMessages
                elif 'errors' in response and len(response['errors']) > 0:
                    # JIRA 6.x error messages are found in this array.
                    error = response['errors']
                else:
                    error = r.text
            except ValueError:
                error = r.text
        raise JIRAError(r.status_code, error, r.url)

Fix for empty errorMessages, moved length check to main logic for deciding which error message to use and added check for 'errors' in the response.
Fix for empty errorMessages, moved length check to main logic for deciding which error
message to use and added check for 'errors' in the response.