Regular update 2020 W18

* Bump `base-notebook`
	* OS version
	* `jupyterlab`
* Bump `scipy-notebook`
	* `beautifulsoup4`
	* `cloudpickle`
	* `dask`
	* `numba`
	* `xlrd`: version specified (it was not the case)
* Bump `datascience-notebook`
	* `r-devtools`
	* `r-forecast`
	* Julia version
	* Test added to check if Julia is correctly installed (`julia --version`)
	* Note: A new version of `r-base` is out `4.0.0` however it cannot be installed yet since dependencies with other packages cannot be resolved.
* Bump `r-notebook`
	* Same as `datascience-notebook` except Julia.
* Bump `all-spark-notebook`
	* `r-sparklyr`

datascience-notebook/test/test_julia.py

@@ -0,0 +1,20 @@
+# Copyright (c) Jupyter Development Team.
+# Distributed under the terms of the Modified BSD License.
+import logging
+
+import pytest
+
+LOGGER = logging.getLogger(__name__)
+
+
+def test_julia(container):
+    """Basic julia test"""
+    LOGGER.info(f"Test that julia is correctly installed ...")
+    running_container = container.run(
+        tty=True, command=["start.sh", "bash", "-c", "sleep infinity"]
+    )
+    command = f"julia --version"
+    cmd = running_container.exec_run(command)
+    output = cmd.output.decode("utf-8")
+    assert cmd.exit_code == 0, f"Command {command} failed {output}"
+    LOGGER.debug(output)