Handle cases when not in environment

Fixes #1

releasedate/jenkins.py

@@ -5,21 +5,47 @@
 import requests
 
 
+class ImproperlyConfigured(Exception):
+    pass
+
+
 def get_previous_tag(tag, build_number):
     return tag.replace(build_number, str(int(build_number) - 1))
 
 
+def get_build_context():
+    """ Obtain info about current CI build for api request:
+
+        * build number
+        * git tag for the build
+        * url of the CI job
+    """
+    try:
+        return {
+            'build_number': env['BUILD_NUMBER'],
+            'build_tag': env['BUILD_TAG'],
+            'job_url': env['JOB_URL']
+        }
+    except KeyError as e:
+        raise ImproperlyConfigured('Missing "%s" env variable. '
+                                   'Launch job via Jenkins, or provide evn variable manually.' % e.message)
+
+
 def run(url=None, repo=None, instance_url=None):
     """ Send POST request to releasedate server after jenkins job is successfully finished"""
     url = url or sys.argv[1]
     repo = repo or sys.argv[2]
     instance_url = instance_url or sys.argv[3] if len(sys.argv) > 3 else instance_url
+    try:
+        context = get_build_context()
+    except ImproperlyConfigured as e:
+        return str(e)
 
     result = requests.post(url, data={
-        'build_number': env['BUILD_NUMBER'],
-        'build_tag': env['BUILD_TAG'],
-        'previous_tag': get_previous_tag(env['BUILD_TAG'], env['BUILD_NUMBER']),
-        'job_url': env['JOB_URL'],
+        'build_number': context['build_number'],
+        'build_tag': context['build_tag'],
+        'previous_tag': get_previous_tag(context['build_tag'], context['build_number']),
+        'job_url': context['job_url'],
         'repo': repo,
         'instance': instance_url,
     })

test_releasedate.py

@@ -61,10 +61,16 @@ def test_client_sent_data(self):
 
         self.assertBodyQueryString(**check_against)
 
-        jenkins.run('http://releasedate-server/', '/path/to/my/repo/', 'myserver')
+        output = jenkins.run('http://releasedate-server/', '/path/to/my/repo/', 'myserver')
+        assert 'OK' in output
         check_against['instance'] = ['myserver']
         self.assertBodyQueryString(**check_against)
 
+    def test_not_in_env(self):
+        output = jenkins.run('http://releasedate-server/', '/path/to/my/repo/')
+        assert 'Missing "BUILD_NUMBER" env variable.' in output
+        assert len(httpretty.latest_requests) == 0
+
 
 class TestRunServer(TestCase):