[test] Add test verifying that writing in the cache fails if not in the output path

beat/core/test/prefix/algorithms/errors/create_file/1.json

+{
+  "language": "python",
+  "splittable": false,
+  "groups": [
+    {
+      "name": "main",
+      "inputs": {
+        "in_data": {
+          "type": "user/single_integer/1"
+        }
+      },
+      "outputs": {
+        "out_data": {
+          "type": "user/single_integer/1"
+        }
+      }
+    }
+  ]
+}

beat/core/test/prefix/algorithms/errors/create_file/1.py

+#!/usr/bin/env python
+# vim: set fileencoding=utf-8 :
+
+###################################################################################
+#                                                                                 #
+# Copyright (c) 2020 Idiap Research Institute, http://www.idiap.ch/               #
+# Contact: beat.support@idiap.ch                                                  #
+#                                                                                 #
+# Redistribution and use in source and binary forms, with or without              #
+# modification, are permitted provided that the following conditions are met:     #
+#                                                                                 #
+# 1. Redistributions of source code must retain the above copyright notice, this  #
+# list of conditions and the following disclaimer.                                #
+#                                                                                 #
+# 2. Redistributions in binary form must reproduce the above copyright notice,    #
+# this list of conditions and the following disclaimer in the documentation       #
+# and/or other materials provided with the distribution.                          #
+#                                                                                 #
+# 3. Neither the name of the copyright holder nor the names of its contributors   #
+# may be used to endorse or promote products derived from this software without   #
+# specific prior written permission.                                              #
+#                                                                                 #
+# THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND #
+# ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED   #
+# WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE          #
+# DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE    #
+# FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL      #
+# DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR      #
+# SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER      #
+# CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,   #
+# OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE   #
+# OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.            #
+#                                                                                 #
+###################################################################################
+
+
+class Algorithm:
+    def process(self, inputs, outputs):
+        with open("/beat/cache/truc.txt", "wt") as file:
+            file.write("Should not write there...")
+
+        # Should not arrive here
+        outputs["out_data"].write(inputs["in_data"].data)
+        return True

beat/core/test/prefix/experiments/errors/user/single/1/write_error.json

+{
+  "analyzers": {
+    "analysis": {
+      "algorithm": "v1/integers_echo_analyzer/1",
+      "inputs": {
+        "in_data": "in"
+      }
+    }
+  },
+  "blocks": {
+    "echo": {
+      "algorithm": "errors/create_file/1",
+      "inputs": {
+        "in_data": "in"
+      },
+      "outputs": {
+        "out_data": "out"
+      }
+    }
+  },
+  "datasets": {
+    "set": {
+      "database": "simple/1",
+      "protocol": "protocol",
+      "set": "set"
+    }
+  },
+  "globals": {
+    "queue": "queue",
+    "environment": {
+      "name": "Python 2.7",
+      "version": "1.3.0"
+    }
+  }
+}

beat/core/test/test_docker_execution.py

@@ -233,3 +233,10 @@ class TestDockerExecution(BaseExecutionMixIn):
         nose.tools.assert_true(
             "[sys] C++ algorithm can't be analyzers" in result["stderr"]
         )
+
+    @slow
+    def test_read_only_error(self):
+        result = self.execute("errors/user/single/1/write_error", [{"out_data": 42}])
+
+        nose.tools.eq_(result["status"], 1)
+        nose.tools.assert_true("Permission denied" in result["user_error"])