title: scrapy-splash does not return the html processed by splash
body: <p>I've installed splash and scrapy-splash in a python virtual environment (Ubuntu 16.04), following the instructions described in the <a href="https://github.com/scrapy-plugins/scrapy-splash" rel="nofollow noreferrer">README</a> file (including the middleware setup etc). Even though, I'm not receiving any error in the log file (apparently), the html returned by the ScrapySplash does not contain html processed by Splash, only the html downloaded by Scrapy (without using splash). </p>
  
  <p>There are some situations where I'm able to obtain the correct html. These are:</p>
  
  <ul>
  <li>Using browser: <a href="http://localhost:8050/" rel="nofollow noreferrer">http://localhost:8050/</a></li>
  <li>Using scrapy shell '<a href="http://localhost:8050/render.html?url=" rel="nofollow noreferrer">http://localhost:8050/render.html?url=</a>..."</li>
  <li>Following the "Why not use the Splash HTTP API directly?" guide in the <a href="https://github.com/scrapy-plugins/scrapy-splash" rel="nofollow noreferrer">README</a> file. </li>
  </ul>
  
  <p>However, scrapy-splash does not return the correct HTML using SplashRequest:</p>
  
  <pre class="lang-py prettyprint-override"><code>yield SplashRequest(url, self.parse, endpoint='render.html', args={'wait': 0.5})
  </code></pre>
  
  <p>This is my configuration in the settings.py file: </p>
  
  <pre class="lang-py prettyprint-override"><code>SPIDER_MIDDLEWARES = {
    'scrapy_splash.SplashDeduplicateArgsMiddleware': 100,
  }
  
  DOWNLOADER_MIDDLEWARES = {
    'scrapy_splash.SplashCookiesMiddleware': 723,
    'scrapy_splash.SplashMiddleware': 725,
    'scrapy.downloadermiddlewares.httpcompression.HttpCompressionMiddleware': 810,
  }
  
  SPLASH_URL = 'http://127.0.0.1:8050/'
  SPLASH_COOKIES_DEBUG = True
  
  DUPEFILTER_CLASS = 'scrapy_splash.SplashAwareDupeFilter'
  HTTPCACHE_STORAGE = 'scrapy_splash.SplashAwareFSCacheStorage'
  </code></pre>
  
  <p>I expect the output of the html processed by splash, but it only returns the html without being processed.</p>
  
  <p>Splash docker message:</p>
  
  <pre><code>process 1: D-Bus library appears to be incorrectly set up; failed to read machine uuid: UUID file '/etc/machine-id' should contain a hex string of length 32, not length 0, with no other text
  See the manual page for dbus-uuidgen to correct this issue.
  qt.network.ssl: QSslSocket: cannot resolve SSLv2_client_method
  qt.network.ssl: QSslSocket: cannot resolve SSLv2_server_method
  2019-04-17 14:35:28.198194 [events] {"timestamp": 1555511728, "status_code": 200, "user-agent": "Scrapy/1.3.3 (+http://scrapy.org)", "client_ip": "172.17.0.1", "load": [0.15, 0.38, 0.35], "rendertime": 5.785578966140747, "active": 0, "fds": 68, "qsize": 0, "method": "POST", "_id": 140284272664528, "path": "/render.html", "args": {"headers": {"Accept": "text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8", "User-Agent": "Scrapy/1.3.3 (+http://scrapy.org)", "Accept-Language": "en", "Cookie": "__cfduid=d035cc38f38ee9f555aec777db4b1b8f81555511718"}, "uid": 140284272664528, "wait": 0.5, "url": "https://www.tampabay.com/events/"}, "maxrss": 159672}
  2019-04-17 14:35:28.198893 [-] "172.17.0.1" - - [17/Apr/2019:14:35:27 +0000] "POST /render.html HTTP/1.1" 200 34075 "-" "Scrapy/1.3.3 (+http://scrapy.org)
  </code></pre>
  
  <p>Scrapy LOG message:</p>
  
  <pre><code>2019-04-17 16:35:18 [scrapy.utils.log] INFO: Scrapy 1.3.3 started (bot: tampabay)
  2019-04-17 16:35:18 [scrapy.utils.log] INFO: Overridden settings: {'NEWSPIDER_MODULE': 'tampabay.spiders', 'ROBOTSTXT_OBEY': True, 'DUPEFILTER_CLASS': 'scrapy_splash.SplashAwareDupeFilter', 'SPIDER_MODULES': ['tampabay.spiders'], 'BOT_NAME': 'tampabay', 'LOG_FILE': 'tampabay.log', 'HTTPCACHE_STORAGE': 'scrapy_splash.SplashAwareFSCacheStorage', 'DOWNLOAD_DELAY': 3}
  2019-04-17 16:35:18 [scrapy.middleware] INFO: Enabled extensions:
  ['scrapy.extensions.logstats.LogStats',
   'scrapy.extensions.telnet.TelnetConsole',
   'scrapy.extensions.corestats.CoreStats']
  2019-04-17 16:35:18 [scrapy.middleware] INFO: Enabled downloader middlewares:
  ['scrapy.downloadermiddlewares.robotstxt.RobotsTxtMiddleware',
   'scrapy.downloadermiddlewares.httpauth.HttpAuthMiddleware',
   'scrapy.downloadermiddlewares.downloadtimeout.DownloadTimeoutMiddleware',
   'scrapy.downloadermiddlewares.defaultheaders.DefaultHeadersMiddleware',
   'scrapy.downloadermiddlewares.useragent.UserAgentMiddleware',
   'scrapy.downloadermiddlewares.retry.RetryMiddleware',
   'scrapy.downloadermiddlewares.redirect.MetaRefreshMiddleware',
   'scrapy.downloadermiddlewares.redirect.RedirectMiddleware',
   'scrapy.downloadermiddlewares.cookies.CookiesMiddleware',
   'scrapy_splash.SplashCookiesMiddleware',
   'scrapy_splash.SplashMiddleware',
   'scrapy.downloadermiddlewares.httpcompression.HttpCompressionMiddleware',
   'scrapy.downloadermiddlewares.stats.DownloaderStats']
  2019-04-17 16:35:18 [scrapy.middleware] INFO: Enabled spider middlewares:
  ['scrapy.spidermiddlewares.httperror.HttpErrorMiddleware',
   'scrapy_splash.SplashDeduplicateArgsMiddleware',
   'scrapy.spidermiddlewares.offsite.OffsiteMiddleware',
   'scrapy.spidermiddlewares.referer.RefererMiddleware',
   'scrapy.spidermiddlewares.urllength.UrlLengthMiddleware',
   'scrapy.spidermiddlewares.depth.DepthMiddleware']
  2019-04-17 16:35:18 [scrapy.middleware] INFO: Enabled item pipelines:
  ['tampabay.pipelines.TampabayPipeline']
  2019-04-17 16:35:18 [scrapy.core.engine] INFO: Spider opened
  2019-04-17 16:35:18 [scrapy.extensions.logstats] INFO: Crawled 0 pages (at 0 pages/min), scraped 0 items (at 0 items/min)
  2019-04-17 16:35:18 [scrapy.extensions.telnet] DEBUG: Telnet console listening on 127.0.0.1:6023
  2019-04-17 16:35:18 [scrapy.core.engine] DEBUG: Crawled (200) &lt;GET https://www.tampabay.com/robots.txt&gt; (referer: None)
  2019-04-17 16:35:18 [scrapy.core.engine] DEBUG: Crawled (404) &lt;GET http://127.0.0.1:8050/robots.txt&gt; (referer: None)
  2019-04-17 16:35:28 [scrapy.core.engine] DEBUG: Crawled (200) &lt;GET https://www.tampabay.com/events/ via http://127.0.0.1:8050/render.html&gt; (referer: None)
  2019-04-17 16:35:28 [tampabay] DEBUG: ############## INSIDE FUNCTION -&gt; parse ############### 
  2019-04-17 16:35:28 [tampabay] DEBUG: EVENTS: 0
  2019-04-17 16:35:28 [scrapy.core.engine] INFO: Closing spider (finished)
  2019-04-17 16:35:28 [scrapy.statscollectors] INFO: Dumping Scrapy stats:
  {'downloader/request_bytes': 1037,
   'downloader/request_count': 3,
   'downloader/request_method_count/GET': 2,
   'downloader/request_method_count/POST': 1,
   'downloader/response_bytes': 35911,
   'downloader/response_count': 3,
   'downloader/response_status_count/200': 2,
   'downloader/response_status_count/404': 1,
   'finish_reason': 'finished',
   'finish_time': datetime.datetime(2019, 4, 17, 14, 35, 28, 333825),
   'log_count/DEBUG': 6,
   'log_count/INFO': 7,
   'response_received_count': 3,
   'scheduler/dequeued': 2,
   'scheduler/dequeued/memory': 2,
   'scheduler/enqueued': 2,
   'scheduler/enqueued/memory': 2,
   'splash/render.html/request_count': 1,
   'splash/render.html/response_count/200': 1,
   'start_time': datetime.datetime(2019, 4, 17, 14, 35, 18, 83737)}
  2019-04-17 16:35:28 [scrapy.core.engine] INFO: Spider closed (finished)
  </code></pre>