teststmpdir: Use variable to share env variable name

The "AVOCADO_TESTS_COMMON_TMPDIR" is an environmental variable name used
to store the location of a common tmpdir. To avoid issues with
typos/name changes let's use the variable in `avocado.core.test` to
share the env variable name everywhere.
Signed-off-by: NLukáš Doktor <ldoktor@redhat.com>

avocado/core/test.py

@@ -47,6 +47,11 @@ else:
     import unittest
 
 
+#: Environment variable used to store the location of a tmpfile which is
+#: preserved across all tests execution (usually in one job)
+COMMON_TMPDIR_NAME = 'AVOCADO_TESTS_COMMON_TMPDIR'
+
+
 class NameNotTestNameError(Exception):
 
     """
@@ -286,7 +291,7 @@ class Test(unittest.TestCase):
         Returns the path of the temporary directory that will stay the
         same for all tests in a given Job.
         """
-        env_var = 'AVOCADO_TESTS_COMMON_TMPDIR'
+        env_var = COMMON_TMPDIR_NAME
         path = os.environ.get(env_var)
         if path is None:
             msg = 'Environment Variable %s is not set.' % env_var

avocado/plugins/teststmpdir.py

@@ -20,6 +20,7 @@ import shutil
 import tempfile
 
 from avocado.core.plugin_interfaces import JobPre, JobPost
+from avocado.core import test
 
 
 class TestsTmpDir(JobPre, JobPost):
@@ -28,7 +29,7 @@ class TestsTmpDir(JobPre, JobPost):
     description = 'Creates a temporary directory for tests consumption'
 
     def __init__(self):
-        self._varname = 'AVOCADO_TESTS_COMMON_TMPDIR'
+        self._varname = test.COMMON_TMPDIR_NAME
         self._dirname = None
 
     def pre(self, job):

selftests/functional/test_teststmpdir.py

@@ -11,6 +11,7 @@ else:
     import unittest
 
 from avocado.core import exit_codes
+from avocado.core import test
 from avocado.utils import process
 from avocado.utils import script
 
@@ -32,14 +33,14 @@ class MyTest(Test):
 """
 
 SIMPLE_SCRIPT = """#!/bin/bash
-mktemp ${AVOCADO_TESTS_COMMON_TMPDIR}/XXXXXX
-if [ $(ls ${AVOCADO_TESTS_COMMON_TMPDIR} | wc -l) == 1 ]
+mktemp ${{{0}}}/XXXXXX
+if [ $(ls ${{{0}}} | wc -l) == 1 ]
 then
     exit 0
 else
     exit 1
 fi
-"""
+""".format(test.COMMON_TMPDIR_NAME)
 
 
 class TestsTmpDirTests(unittest.TestCase):
@@ -63,6 +64,9 @@ class TestsTmpDirTests(unittest.TestCase):
                          "%d:\n%s" % (cmd_line, expected_rc, result))
         return result
 
+    @unittest.skipIf(test.COMMON_TMPDIR_NAME in os.environ,
+                     "%s already set in os.environ"
+                     % test.COMMON_TMPDIR_NAME)
     def test_tests_tmp_dir(self):
         cmd_line = ("./scripts/avocado run --sysinfo=off "
                     "--job-results-dir %s %s %s" %