support skipping interpreters if any are missing

This implements the option --skip-missing-interpreters. If this option is
passed to tox, the tests won't fail if interpreters are missing. The exit
status will be 0 if all tests pass but interpreters were missing.

3 files changed, 29 insertions, 1 deletions

diff --git a/tests/test_z_cmdline.py b/tests/test_z_cmdline.py
index 537db5d..6d2575f 100644
--- a/tests/test_z_cmdline.py
+++ b/tests/test_z_cmdline.py
@@ -229,6 +229,22 @@ def test_unknown_interpreter(cmd, initproj):
         "*ERROR*InterpreterNotFound*xyz_unknown_interpreter*",
     ])
 
+def test_skip_unknown_interpreter(cmd, initproj):
+    initproj("interp123-0.5", filedefs={
+        'tests': {'test_hello.py': "def test_hello(): pass"},
+        'tox.ini': '''
+            [testenv:python]
+            basepython=xyz_unknown_interpreter
+            [testenv]
+            changedir=tests
+        '''
+    })
+    result = cmd.run("tox", "--skip-missing-interpreters")
+    assert not result.ret
+    result.stdout.fnmatch_lines([
+        "*SKIPPED*InterpreterNotFound*xyz_unknown_interpreter*",
+    ])
+
 def test_unknown_dep(cmd, initproj):
     initproj("dep123-0.7", filedefs={
         'tests': {'test_hello.py': "def test_hello(): pass"},
diff --git a/tox/_cmdline.py b/tox/_cmdline.py
index 192658d..5d58a18 100644
--- a/tox/_cmdline.py
+++ b/tox/_cmdline.py
@@ -222,6 +222,9 @@ class Reporter(object):
     def error(self, msg):
         self.logline("ERROR: " + msg, red=True)
 
+    def skip(self, msg):
+        self.logline("SKIPPED:" + msg, yellow=True)
+
     def logline(self, msg, **opts):
         self._reportedlines.append(msg)
         self.tw.line("%s" % msg, **opts)
@@ -461,7 +464,14 @@ class Session:
         retcode = 0
         for venv in self.venvlist:
             status = venv.status
-            if status and status != "skipped tests":
+            if isinstance(status, tox.exception.InterpreterNotFound):
+                msg = "  %s: %s" %(venv.envconfig.envname, str(status))
+                if self.config.option.skip_missing_interpreters:
+                    self.report.skip(msg)
+                else:
+                    retcode = 1
+                    self.report.error(msg)
+            elif status and status != "skipped tests":
                 msg = "  %s: %s" %(venv.envconfig.envname, str(status))
                 self.report.error(msg)
                 retcode = 1
diff --git a/tox/_config.py b/tox/_config.py
index 2753780..57df84d 100644
--- a/tox/_config.py
+++ b/tox/_config.py
@@ -129,6 +129,8 @@ def prepare_parse(pkgname):
              "'pytest<2.7' or 'django>=1.6'.")
     parser.add_argument("--sitepackages", action="store_true",
         help="override sitepackages setting to True in all envs")
+    parser.add_argument("--skip-missing-interpreters", action="store_true",
+        help="don't fail tests for missing interpreters")
 
     parser.add_argument("args", nargs="*",
         help="additional arguments available to command positional substitution")