NonExistentTimeError after Resample
#### Code Sample
```python
import pandas as pd
import numpy as np
import pytz 
index=pd.date_range('2017-03-12', '2017-03-12 1:45:00', freq='15T')
my_series = pd.Series(np.zeros(len(index)), index=index)
my_series = my_series.tz_localize('US/Pacific')
my_series.resample('900S').mean()
```

Some Version Information:

Python: 3.6.2 
pandas: 0.22.0 
pytz: 2017.3 
numpy: 1.13.0

#### Problem description

The above code returns the error message NonExistentTimeError: 2017-03-12 02:00:00; however, the input series only contains timestamps up to 2017-03-12 01:45:00. Does anyone understand why this error is occurring? If so, how can I address the problem?

