Error with download of soil moisture dataset

[HelenClifton]

Expected behavior

@papesci Using mac machine, selected soil moisture dataset.
Expected it to download.

Actual behavior

Task failed with error:
Internal Error (Invalid response)
Invalid response (not JSON-serializable)

As a note, same dataset will not download on windows machine, but there is a different error, see #667

Steps to reproduce the problem

1.Select esacci.SOILMOISTURE.day.L3S.SSMV.multi-sensor.multi-platform.COMBINED.03-2.r1
2.Select Download Dataset to Local option with:
Time Constraint: 2007-01-01 to 2007-12-31
Region Constraint:
o Lon. from: 72
o Lon. to: 85
o Lat. from: 8
o Lat. to: 17
Variables Constraint: sm, sm_uncertainty

Specifications

MacBook Pro OS X version 10.9.5
cate-2.0.0-dev.15

[HelenClifton]

@papesci , @forman I've just repeated this using exactly the same machine and the same version of cate, and this time the dataset downloaded successfully with no error. I've got no idea why.
But if the error can't be reproduced, the issue should be closed.

[HelenClifton]

@papesci It was seen again, on a Windows machine this time, running cate-2.0.0.-dev.16.
Tried the download again a few minutes later, and then the error no longer occurred.

[HelenClifton]

@papesci Am closing this one.
Can be re-opened if the problem is seen again.