Catch ValueError during network discovery for when JSON parsing fails
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### Observed behavior
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Description of the behavior that was observed, including screenshots or other references when applicable
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When trying to import content channels (from local network or internet), no error message is produced even though the connection isn't established. (The "trying to connect" message stays on forever) This happens when there is a typo in the address. (I used kolibri-demo.learningequality.omg)  When there's no internet, an error message DOES get produced. 

### Expected behavior
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Description of what behavior was expected but did not occur
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An error message should've been produced.

### User-facing consequences
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The user will not know how long they have to wait to see if the connection is being established.

### Errors and logs
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01:10 info: something happened
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…

### Steps to reproduce
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Import content channels from local network or internet >input "kolibri-demo.learningequality.omg" or something else with a typo in it.

### Context
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Kolibri version: 0.14.3
Operating system: Android 5.1
Browser: Android App
Device: BLU Advance 5.0

diff --git a/kolibri/core/discovery/utils/network/client.py b/kolibri/core/discovery/utils/network/client.py
index 431e6dac03..727906f572 100644
--- a/kolibri/core/discovery/utils/network/client.py
+++ b/kolibri/core/discovery/utils/network/client.py
@@ -55,6 +55,10 @@ class NetworkClient(object):
                     return response.url.rstrip("/").replace("api/public/info", "")
             except (requests.RequestException) as e:
                 logger.info("Unable to connect: {}".format(e))
+            except ValueError:
+                logger.info(
+                    "Invalid JSON returned when attempting to connect to a remote server"
+                )
 
         # we weren't able to connect to any of the URL variations, so all we can do is throw
         raise errors.NetworkLocationNotFound()
['kolibri/core/discovery/utils/network/client.py']