Django项目配置xadmin 无法加载主题切换功能

开启主题切换功能，只需做如下设置，此种设置仅有两种默认的bootstrap主题：
adminx.py
class BaseSetting(object):
# 添加主题功能
enable_themes = True
#使用更多主题
use_bootswatch = True
解决办法：
阅读xadmin/plugins/themes.py源码进行错误排查，基本锁定错误发生在第75行。在访问bootswatch资源时超时。每次服务重启，第一次进入系统都要等1~2分钟也是因为这里的问题

浏览器访问https://bootswatch.com/api/3.json查看所有可用主题。将可用主题的name，css参数记录到user_themes参数中即可。

修改为：
class BaseSetting(object):
# 添加主题功能
enable_themes = True
use_bootswatch = True
user_themes = [{'name': 'Cerulean', 'css': 'https://bootswatch.com/3/cerulean/bootstrap.css'},
{'name': 'Cosmo', 'css': 'https://bootswatch.com/3/cosmo/bootstrap.css'},
{'name': 'Cyborg', 'css': 'https://bootswatch.com/3/cyborg/bootstrap.css'},
{'name': 'Darkly', 'css': 'https://bootswatch.com/3/darkly/bootstrap.css'},
{'name': 'Flatly', 'css': 'https://bootswatch.com/3/flatly/bootstrap.css'},
{'name': 'Journal', 'css': 'https://bootswatch.com/3/journal/bootstrap.css'},
{'name': 'Lumen', 'css': 'https://bootswatch.com/3/lumen/bootstrap.css'},
{'name': 'Paper', 'css': 'https://bootswatch.com/3/paper/bootstrap.css'},
{'name': 'Readable', 'css': 'https://bootswatch.com/3/readable/bootstrap.css'},
{'name': 'Sandstone', 'css': 'https://bootswatch.com/3/sandstone/bootstrap.css'},
{'name': 'Simplex', 'css': 'https://bootswatch.com/3/simplex/bootstrap.css'},
{'name': 'Slate', 'css': 'https://bootswatch.com/3/slate/bootstrap.css'},
{'name': "Superhero", 'css': "https://bootswatch.com/3/superhero/bootstrap.css"},
{'name': "United", 'css': "https://bootswatch.com/3/united/bootstrap.css"},
{'name': "Yeti", 'css': "https://bootswatch.com/3/yeti/bootstrap.css"},
]
themes.py中
def block_top_navmenu(self, context, nodes):

    themes = [
        {'name': _(u"Default"), 'description': _(u"Default bootstrap theme"), 'css': self.default_theme},
        {'name': _(u"Bootstrap2"), 'description': _(u"Bootstrap 2.x theme"), 'css': self.bootstrap2_theme},
        ]
    select_css = context.get('site_theme', self.default_theme)

    if self.user_themes:
        themes.extend(self.user_themes)

    if self.use_bootswatch:
        ex_themes = cache.get(THEME_CACHE_KEY)
        if ex_themes:
            themes.extend(json.loads(ex_themes))
        else:
            ex_themes = []
            try:
                headers = {"Accept": "application/json", "User-Agent": self.request.META['HTTP_USER_AGENT']}
                content = requests.get("https://bootswatch.com/api/3.json", headers=headers)
                if six.PY3:
                    content = content.text.decode()
                watch_themes = json.loads(content.text)['themes']
                ex_themes.extend([{'name': t['name'], 'description': t['description'], 'css': t['cssMin'],
                                   'thumbnail': t['thumbnail']} for t in watch_themes])
            except Exception as e:
                print(e)

            cache.set(THEME_CACHE_KEY, json.dumps(ex_themes), 24 * 3600)
            themes.extend(ex_themes)

修改为：
def block_top_navmenu(self, context, nodes):

        themes = [
            {'name': _(u"Default"), 'description': _(u"Default bootstrap theme"), 'css': self.default_theme},
            {'name': _(u"Bootstrap2"), 'description': _(u"Bootstrap 2.x theme"), 'css': self.bootstrap2_theme},
        ]
        select_css = context.get('site_theme', self.default_theme)

        if self.user_themes:
            themes.extend(self.user_themes)

        if self.use_bootswatch:
            ex_themes = cache.get(THEME_CACHE_KEY)
            if ex_themes:
                themes.extend(json.loads(ex_themes))
            else:
                ex_themes = []
                try:
                    flag = False  # 假如为True使用原来的代码，假如为Flase，使用requests库来访问
                    if flag:
                        h = httplib2.Http()
                        resp, content = h.request("https://bootswatch.com/api/3.json", 'GET', '',
                                                  headers={"Accept": "application/json",
                                                           "User-Agent": self.request.META['HTTP_USER_AGENT']})
                        if six.PY3:
                            content = content.decode()
                        watch_themes = json.loads(content)['themes']
                    else:
                        content = requests.get("https://bootswatch.com/api/3.json")
                        if six.PY3:
                            content = content.text.decode()
                        watch_themes = json.loads(content.text)['themes']
                    ex_themes.extend([
                        {'name': t['name'], 'description': t['description'],
                         'css': t['cssMin'], 'thumbnail': t['thumbnail']}
                        for t in watch_themes])
                except Exception as e:
                    print(e)

                cache.set(THEME_CACHE_KEY, json.dumps(ex_themes), 24 * 3600)
                themes.extend(ex_themes)