SDWebImage 加载图片不显示问题 --- 难以想象的BUG

今天碰到一个BUG

 [self.headImage sd_setImageWithURL:[NSURL URLWithString:_model.EAImg] placeholderImage:[UIImage imageNamed:@"gd"]];

多么正常的异步加载图片，他就不正常的显示了，只显示placeholderImage，其他页面倒是可以正常显示，区别就是图片的URL；这个URL是http的，别的是HTTPS；查了一些资料，说是URL问题；解决方法也有；

[self.headImage sd_setImageWithURL:[NSURL URLWithString:_model.EAImg] placeholderImage:[UIImage imageNamed:@"gd"] completed:^(UIImage *image, NSError *error, SDImageCacheType cacheType, NSURL *imageURL) {
        //在这里输出下error
    }];

error：

一、Error Domain=NSURLErrorDomain Code=403 “The operation couldn’t be completed. (NSURLErrorDomain error 403.)”

 //SDWebImage 一个难以想象的BUG
    NSString *userAgent = @"";
    userAgent = [NSString stringWithFormat:@"%@/%@ (%@; iOS %@; Scale/%0.2f)", [[[NSBundle mainBundle] infoDictionary] objectForKey:(__bridge NSString *)kCFBundleExecutableKey] ?: [[[NSBundle mainBundle] infoDictionary] objectForKey:(__bridge NSString *)kCFBundleIdentifierKey], [[[NSBundle mainBundle] infoDictionary] objectForKey:@"CFBundleShortVersionString"] ?: [[[NSBundle mainBundle] infoDictionary] objectForKey:(__bridge NSString *)kCFBundleVersionKey], [[UIDevice currentDevice] model], [[UIDevice currentDevice] systemVersion], [[UIScreen mainScreen] scale]];
    
    if (userAgent) {
        if (![userAgent canBeConvertedToEncoding:NSASCIIStringEncoding]) {
            NSMutableString *mutableUserAgent = [userAgent mutableCopy];
            if (CFStringTransform((__bridge CFMutableStringRef)(mutableUserAgent), NULL, (__bridge CFStringRef)@"Any-Latin; Latin-ASCII; [:^ASCII:] Remove", false)) {
                userAgent = mutableUserAgent;
            }
        }
        [[SDWebImageDownloader sharedDownloader] setValue:userAgent forHTTPHeaderField:@"User-Agent"];
    }
    [self.headImage sd_setImageWithURL:[NSURL URLWithString:_model.EAImg] placeholderImage:[UIImage imageNamed:@"gd"]];

二、Error Domain=NSURLErrorDomain Code=406 “The operation couldn’t be completed. (NSURLErrorDomain error 406.)”

//请求之前加上这句话

  [SDWebImageDownloader.sharedDownloader setValue:@"text/html,application/xhtml+xml,application/xml;q=0.9,image/webp,*/*;q=0.8"
                                     forHTTPHeaderField:@"Accept"];