Add Syntastic statusline

Refs #376, #639.
Closes #451.

powerline/config_files/themes/vim/default.json

@@ -58,6 +58,11 @@
 				"name": "modified_indicator",
 				"before": " "
 			},
+			{
+				"exclude_modes": ["nc"],
+				"module": "powerline.segments.plugin.syntastic",
+				"name": "syntastic"
+			},
 			{
 				"type": "string",
 				"highlight_group": ["background"],

powerline/segments/plugin/syntastic.py

@@ -0,0 +1,28 @@
+# vim:fileencoding=utf-8:noet
+
+import vim
+
+from powerline.segments.vim import window_cached
+
+
+@window_cached
+def syntastic(pl):
+	if not int(vim.eval('exists("g:SyntasticLoclist")')):
+		return
+	has_errors = int(vim.eval('g:SyntasticLoclist.current().hasErrorsOrWarningsToDisplay()'))
+	if not has_errors:
+		return
+	errors = vim.eval('g:SyntasticLoclist.current().errors()')
+	warnings = vim.eval('g:SyntasticLoclist.current().warnings()')
+	segments = []
+	if errors:
+		segments.append({
+			'contents': 'ERR:  {line} ({num}) '.format(line=errors[0]['lnum'], num=len(errors)),
+			'highlight_group': ['syntastic.error', 'error', 'background'],
+			})
+	if warnings:
+		segments.append({
+			'contents': 'WARN:  {line} ({num}) '.format(line=warnings[0]['lnum'], num=len(warnings)),
+			'highlight_group': ['syntastic.warning', 'warning', 'background'],
+			})
+	return segments