tools: updater: add exceptions for errors

Add custom exception for errors per TODO comments.

Change-Id: I14b89afe816724ff2bdb1761ef6e6a0a8217feed
Signed-off-by: Patrick Venture <venture@google.com>
diff --git a/tools/tool_errors.hpp b/tools/tool_errors.hpp
new file mode 100644
index 0000000..af99c2c
--- /dev/null
+++ b/tools/tool_errors.hpp
@@ -0,0 +1,18 @@
+#pragma once
+
+#include <exception>
+#include <string>
+
+class ToolException : public std::exception
+{
+  public:
+    explicit ToolException(const std::string& message) : message(message){};
+
+    virtual const char* what() const noexcept override
+    {
+        return message.c_str();
+    }
+
+  private:
+    std::string message;
+};