added signatures subcommand

tests/testcommon.py

@@ -0,0 +1,34 @@
+#!/usr/bin/env python3
+#
+# Copyright (C) 2017, Michael Poehn <michael.poehn@fsfe.org>
+#
+# This program is free software: you can redistribute it and/or modify
+# it under the terms of the GNU Affero General Public License as published by
+# the Free Software Foundation, either version 3 of the License, or
+# (at your option) any later version.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU Affero General Public License for more details.
+#
+# You should have received a copy of the GNU Affero General Public License
+# along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+import os
+
+
+class TmpCwd():
+    """Context-manager for temporarily changing the current working
+    directory.
+    """
+
+    def __init__(self, new_cwd):
+        self.new_cwd = new_cwd
+
+    def __enter__(self):
+        self.orig_cwd = os.getcwd()
+        os.chdir(self.new_cwd)
+
+    def __exit__(self, a, b, c):
+        os.chdir(self.orig_cwd)