input: Write a function to develop a machine learning model in Python for predicting the winning team of football matches. Use data from the past 5 years of the Premier League. The function should load the data, select features, split the data into training and test sets, train a Gradient Boosting Classifier, and evaluate the model by printing the score. If the data file "data.csv" is not found, the function should return a message "File not found".
  
  assert develop_winning_team_model()=="File not found"
output: def develop_winning_team_model():
      import pandas as pd
      from sklearn.model_selection import train_test_split
      from sklearn.ensemble import GradientBoostingClassifier
      try:
          data = pd.read_csv("data.csv")
          features = data.drop(columns=['winning_team'])
          target = data['winning_team']
          X_train, X_test, y_train, y_test = train_test_split(features, target, test_size=0.2, random_state=42)
          model = GradientBoostingClassifier()
          model.fit(X_train, y_train)
          score = model.score(X_test, y_test)
          print(score)
      except FileNotFoundError:
          return "File not found"