Influx: Error when querying datastreams with special characters

When querying datastreams with "special" characters (others than 0-9, a-z and _), the systems raises an

HTTP 500 Internal server error

Example:

https://timeseries.gfz-potsdam.de/tsmdl/api/v1/Datasources(influxdb_01:tereno_no)/Things(heydenhof)/Datastreams(SoilTemperature_0.1m)/Observations

This is caused by the unescaped usage of the datastream variable in app/gfz/influx.py in the method get_observations. Trying it out with the Influx client I can reproduce the error:

First query from the method:

> SELECT SoilTemperature_0.1m FROM heydenhof WHERE time >= '2013-01-29' and time <= '2014-04-14';
ERR: error parsing query: found .1, expected FROM at line 1, char 25

Second query from the method:

> SELECT value AS SoilTemperature_0.1m FROM heydenhof_SoilTemperature_0.1m WHERE time >= '2013-01-29' and time <= '2014-04-14';
ERR: error parsing query: found .1, expected FROM at line 1, char 34

When I put the datastream into quotes, both queries don't return an error and the second query returns data, as expected:

> SELECT value AS "SoilTemperature_0.1m" FROM "heydenhof_SoilTemperature_0.1m" WHERE time >= '2013-01-29' and time <= '2014-04-14' LIMIT 3;

name: heydenhof_SoilTemperature_0.1m
time                SoilTemperature_0.1m
----                --------------------
1359417600000000000 0
1359417600000000000 0
1359418500000000000 0