Update client.py

Author: kunalshah03

rufus/client.py

@@ -9,12 +9,12 @@ def __init__(self, api_key: str = None):
         load_dotenv()
         self.api_key = api_key or os.getenv('RUFUS_API_KEY')
         if not self.api_key:
-            raise ValueError("API key is required. Set RUFUS_API_KEY environment variable")
+            raise ValueError("API key is required. Set the 'RUFUS_API_KEY' environment variable.")
         self.scraper = WebScraper()
         self.processor = ContentProcessor(api_key=self.api_key)
 
     def scrape(self, url: str, instructions: str = None) -> List[Dict]:
         if not url.startswith(('http://', 'https://')):
-            raise ValueError("Invalid URL format")
+            raise ValueError("URL must start with 'http://' or 'https://'.")
         raw_content = self.scraper.crawl(url)
         return self.processor.process(raw_content, instructions)