oh yeah let's not crash on basic mistakes

noble.py

@@ -1,13 +1,20 @@
 #!/usr/bin/env python3
 import pystache, sys, yaml
 
+def DieIf(cond, *message, **kwargs):
+    if cond:
+        print(sys.argv[0] + ":", *message, **kwargs)
+        sys.exit(1)
+
 inData = yaml.safe_load(sys.stdin.read())
+DieIf(len(sys.argv)==1, "no template specified")
 template = open(sys.argv[1], 'r').read()
 data = {'scheme-name': inData.get('scheme', 'Untitled'),
         'scheme-author': inData.get('author', 'Anonymous'),
         'scheme-slug': '<stdin>'}
 
 for i in ["base%02X" % x for x in range(16)]:
+    DieIf(i not in inData, "missing color %s" % i)
     colorHex = [inData[i][x*2:x*2+2] for x in range(3)]
     color = [int(x, 16) for x in colorHex]
     data[i + "-hex"] = inData[i]