Unable to scan common file types

### Description
I am running scancode against a code base of many files, many directories deep. It seems to not be able to scan several text file types. The only way I can get the scan to run and produce output is to --ignore all types that it's unable to scan.

`Setup plugins...

Collect file inventory...
Scan files for: licenses with 4 process(es)...
[####################] 10562
Scanning done.
Some files failed to scan properly:
.dat
.input
.c
.xml
.csv
.h
.txt`

### System configuration
* Running on RHEL7 OS
* scancode-toolkit version is the latest release (3.0.2)
* I downloaded the .zip file for the release then followed the instructions (initially running scancode --help)