Avoid stack trace on missing XML root node, zenhob#25.

I've gotten a report of a stack trace. I do not know the cause yet,
but uncaught exceptions are not useful, complaining and showing the
payload might be.

lib/hcl.rb

@@ -39,21 +39,26 @@ def self.command *args
   end
 
   def run
-    if @command
-      if respond_to? @command
-        result = send @command, *@args
-        if not result.nil?
-          if result.respond_to? :to_a
-            puts result.to_a.join(', ')
-          elsif result.respond_to? :to_s
-            puts result
+    begin
+      if @command
+        if respond_to? @command
+          result = send @command, *@args
+          if not result.nil?
+            if result.respond_to? :to_a
+              puts result.to_a.join(', ')
+            elsif result.respond_to? :to_s
+              puts result
+            end
           end
+        else
+          raise UnknownCommand, "unrecognized command `#{@command}'"
         end
       else
-        raise UnknownCommand, "unrecognized command `#{@command}'"
+        show
       end
-    else
-      show
+    rescue TimesheetResource::Failure => e
+      puts "Internal failure. #{e}"
+      exit 1
     end
   end
 

lib/hcl/day_entry.rb

@@ -2,6 +2,7 @@
 class HCl 
   class DayEntry < TimesheetResource
     include Utility
+
     # Get the time sheet entries for a given day. If no date is provided
     # defaults to today.
     def self.all date = nil
@@ -15,6 +16,7 @@ def to_s
 
     def self.from_xml xml
       doc = REXML::Document.new xml
+      raise Failure, "No root node in XML document: #{xml}" if doc.root.nil?
       Task.cache_tasks doc
       doc.root.elements.collect('//day_entry') do |day|
         new xml_to_hash(day)

lib/hcl/timesheet_resource.rb

@@ -1,5 +1,7 @@
 class HCl
   class TimesheetResource
+    class Failure < Exception; end
+
     def self.configure opts = nil
       if opts
         self.login = opts['login']