requests.exceptions.HTTPError: 403 Client Error: Forbidden for url

The error:
```python
requests.exceptions.HTTPError: 403 Client Error: Forbidden for url: https://data.alpaca.markets/v1/bars/5Min?symbols=AAPL&limit=1000&start=2020-01-01T00%3A00%3A00-04%3A00&end=2020-01-11T23%3A00%3A00-04%3A00
```

My code:
```python
from datetime import datetime, timedelta
import pandas as pd
from tqdm import tqdm
import time

import alpaca_trade_api as tradeapi

def break_period_in_dates_list(start_date, end_date, days_per_step):
'''Break period between start_date and end_date in steps of days_per_step days.'''
step_start_date = start_date
delta = timedelta(days=days_per_step)
dates_list = []
while end_date > (step_start_date + delta):
dates_list.append((step_start_date, step_start_date+delta))
step_start_date += delta
dates_list.append((step_start_date, end_date))
return dates_list

def format_timestep_list(timestep_list):
'''Format dates in ISO format plus timezone. Note that first day starts at 00:00 and last day ends at 23:00hs.'''
for i, d in enumerate(timestep_list):
timestep_list[i] = (d[0].isoformat() + '-04:00', (d[1].isoformat().split('T')[0] + 'T23:00:00-04:00'))
return timestep_list

def get_df_from_barset(barset):
'''Create a Pandas Dataframe from a barset.'''
df_rows = []
for symbol, bar in barset.items():
rows = bar.__dict__.get('_raw')
for i, row in enumerate(rows):
row['symbol'] = symbol
df_rows.extend(rows)

return pd.DataFrame(df_rows)

def download_data(aps, symbols, start_date, end_date, filename='data.csv'):
'''Download data from REST manager for list of symbols, from start_date at 00:00hs to end_date at 23:00hs,
and save it to filename as a csv file.'''
timesteps = format_timestep_list(break_period_in_dates_list(start_date, end_date, 10))
df = pd.DataFrame()

for timestep in tqdm(timesteps):
barset = aps.get_barset(symbols, '5Min', limit=1000, start=timestep[0], end=timestep[1])
df = df.append(get_df_from_barset(barset))
time.sleep(0.1)

df.to_csv(filename)


# Call method.
aps = tradeapi.REST(key_id = '8234d8a5df686d085318b14fb6302889',
secret_key = '60d7290794ade03e17595dcebb6d47b58c1aea19',
base_url = 'https://paper-api.alpaca.markets')

download_data(aps = aps,
symbols = ['AAPL'],
start_date = datetime.strptime('01/01/20', '%d/%m/%y'),
end_date = datetime.strptime('01/02/20', '%d/%m/%y'),
filename = 'test.csv')

```

OS: Windows 10
Browser: Edge
Python: 3.8.3

Thanks for the help.