Merge branch 'bschubert/fix-command-sandbox' into 'master'

Check is command is a str and replace by list before checking existence

Closes #728

See merge request !898

buildstream/sandbox/_sandboxbwrap.py

@@ -66,15 +66,15 @@ class SandboxBwrap(Sandbox):
         cwd = self._get_work_directory(cwd=cwd)
         env = self._get_environment(cwd=cwd, env=env)
 
+        # Convert single-string argument to a list
+        if isinstance(command, str):
+            command = [command]
+
         if not self._has_command(command[0], env):
             raise SandboxError("Staged artifacts do not provide command "
                                "'{}'".format(command[0]),
                                reason='missing-command')
 
-        # We want command args as a list of strings
-        if isinstance(command, str):
-            command = [command]
-
         # Create the mount map, this will tell us where
         # each mount point needs to be mounted from and to
         mount_map = MountMap(self, flags & SandboxFlags.ROOT_READ_ONLY)

buildstream/sandbox/_sandboxchroot.py

@@ -57,15 +57,15 @@ class SandboxChroot(Sandbox):
         cwd = self._get_work_directory(cwd=cwd)
         env = self._get_environment(cwd=cwd, env=env)
 
+        # Convert single-string argument to a list
+        if isinstance(command, str):
+            command = [command]
+
         if not self._has_command(command[0], env):
             raise SandboxError("Staged artifacts do not provide command "
                                "'{}'".format(command[0]),
                                reason='missing-command')
 
-        # Command must be a list
-        if isinstance(command, str):
-            command = [command]
-
         stdout, stderr = self._get_output()
 
         # Create the mount map, this will tell us where

buildstream/sandbox/_sandboxdummy.py

@@ -33,6 +33,10 @@ class SandboxDummy(Sandbox):
         cwd = self._get_work_directory(cwd=cwd)
         env = self._get_environment(cwd=cwd, env=env)
 
+        # Convert single-string argument to a list
+        if isinstance(command, str):
+            command = [command]
+
         if not self._has_command(command[0], env):
             raise SandboxError("Staged artifacts do not provide command "
                                "'{}'".format(command[0]),