Data integrity is so important. We need your help to make sure we've got it.

You've received two different sets of data, each claiming to be the reliable source of truth. Write a ruby command line tool that can parse the two sets of data and output any discrepancies. 

The data sits in two CSV files, each with three columns:

`Account Email, YouTube Channel, Subscriber Count`

You can assume the account emails are the same between files and reliable. 

Your command line tool should take the two files and a third optional concern as arguments.

**Example Usage:**
```
yt_data_checker [file1.csv] [file2.csv] [concern]
* concern is optional
```

**Options:**
 - files: Required. The two sets of data are provided below
 - concerns: Optional `subscriber_count` or `channel_ownership`

**Output:**
- Output a list of account emails with a discrepancy, line delimited
- If a concern is provided, only output discrepancies related to that data
- If no concern is provided, output all the unique discrepancies

Example Output:
```
test_1@gmail.com
test_2@gmail.com
test_3@gmail.com
```

*Note:* since these files have been passed around and maintained by different people, the formatting is not consistent. 
Also YouTube ids can start with an optional `UC`.

CSV 1
```
Account Email, YouTube Channel, Subscriber Count
test_1@gmail.com,UCWBKJ1RNeKTPII34pc6UyUg,28443
test_2@gmail.com,5OXObSqKlu01WtG0GTUq2g,13
test_3@gmail.com,7iTbphgUFuJarHcAHMGduQ,1365
test_4@gmail.com,http://www.youtube.com/channel/UCe09gaA8UCiamw0RQaHuHJw,5
test_5@gmail.com,https://www.youtube.com/channel/UClELwfTibQ78MAVyVi6twCg,1477
test_6@gmail.com,https://www.youtube.com/channel/UC1OFDlfdRb6ma1ZGZd07gWA,3590503
test_7@gmail.com,https://www.youtube.com/channel/UCfHRX7ihY8WnSV53NnpKOvQ,54065
test_8@gmail.com,6cf7Ad_qowX9qeQfD5dT8g,2831
test_9@gmail.com,tIRU_vvyQmUADgAt31n7Xg,564
test_10@gmail.com,Qv9Wo4D2g8tMhH3lGcxiWg,282
test_11@gmail.com,s4cgIKR4SfglgNQGARgsHA,56632
test_12@gmail.com,kRkD16_ps8mZvkZHnby5oA,26582
test_13@gmail.com,pfLKSzjkVsBqIHNbl8Mz6A,428
test_14@gmail.com,oG6lsYx4dhedb0ZjL2O_HQ,5495
test_15@gmail.com,http://youtube.com/channel/UCXApAnHLoStKPlFR9_KoBKw,6
test_16@gmail.com,1eyHg00NjjbFMeF9Ol1Zew,29126
test_17@gmail.com,http://www.youtube.com/channel/UCGfVjOZE8TTR6L1ylG6lHSg,8366
test_18@gmail.com,RJ-d6DiO6raIEddFnlrubQ,132
test_19@gmail.com,q6N_kqiCjE-KqDmoWgXKYA,"26"
test_20@gmail.com,33PJanBSN4WfosXHVkA9_A,2371
test_21@gmail.com,B5ZnX_2hTTP5tTuPmOk3uA,344
test_22@gmail.com,A8E2__IHw9UZhEeHrTEnJA,339
test_23@gmail.com,UCfmVQFPh1KVkCvuvQjnRrxA,42953
test_24@gmail.com,OiVONk5g_VCxXtP2som4yA,172
test_25@gmail.com,ZNw2suHUu1t9NyHB0DolbA,10
test_26@gmail.com,ZtvdCKWWq8AkTZW1RXpy1A,"2,216"
test_27@gmail.com,http://www.youtube.com/channel/UCJCM8kLrPjgPcEJEuIV-ELw,1402
test_28@gmail.com,http://www.youtube.com/channel/UCDi_A4XTSiD5hCO3-6R6OqA,2570
test_29@gmail.com,tUCA0-v2fjxOOPyA84nJlg,1434
test_30@gmail.com,5ZiUupQKOcEx1gvShKS6Bg,688
test_31@gmail.com,UCzSS4r4fkYgvXL6bWCRwegg,25
test_32@gmail.com,fq9aGE_r1TvTfYWpxEI0_Q,180
test_33@gmail.com,youtube.com/channel/UC6WLScIs2J8VnFulIn79Nfw,534
test_34@gmail.com,http://www.youtube.com/channel/UC8bKzySZjA4Eiir7JvBSkEg,89
test_35@gmail.com,youtube.com/channel/UCQeUfLM907YOxA_9_jIiung,1076
test_36@gmail.com,http://www.youtube.com/channel/UCb95qCSx8rO7U0P0oE6RcvA,503
test_37@gmail.com,w53zi4ftVPYpqKTQUoxfKw,254
test_38@gmail.com,uyFiGMNqQo-nfBX5jY5ZOA,20
test_39@gmail.com,KPsyZ9KQiXktdGK2jRaTwQ,301
test_40@gmail.com,GfCFvRsJfXXgPD1wfrI9wA,644
test_41@gmail.com,e7gOaF5-tH7I3NocgLnhAA,21507
test_42@gmail.com,jXe6LuyALURdEdRBOn8C5A,286
test_43@gmail.com,cLDyZ4ESTq6TQGbc2M1Zig,112
test_44@gmail.com,-Zh14hU-5p58lilWNwyQlg,33
test_45@gmail.com,YLCka_OXQZtoBJZ5pW9sFg,2000
test_46@gmail.com,_lpDjhfkyaAr1Fd6AoMXQw,10
test_47@gmail.com,UCEL6PQjvKuk2-6sTaUmub8A,89
test_48@gmail.com,sbo6gAIwSELM1vApwRw4ng,"244"
test_49@gmail.com,X0ZEkd41kOTZ_2qRHViSQw,54
test_50@gmail.com,http://www.youtube.com/channel/UCsR5ZMY4gyAuCUTMkxPocrQ,4
test_51@gmail.com,v3jmHLil11QvVzXxm18KHg,59
test_52@gmail.com,hJbZilh7YcrnajYJ-gsLqw,84
test_53@gmail.com,Cnms8EieLvB6oNLXBgIGNQ,138902
test_54@gmail.com,tTIo7Mi2KuZTwoCys4Cdhw,1
test_55@gmail.com,KjvSEotHjQFYjRwCWJGSdQ,5
test_56@gmail.com,YVAY2qVpaIzVWA56nIkJtA,766
test_57@gmail.com,Phv_Fz6YkjqbWI11IhScOQ,89
test_58@gmail.com,UCiQ4x3FbxB9yPETGlvevbJQ,246
test_59@gmail.com,http://youtube.com/channel/UCg0zJnmieAtkq0evFcgt97w,29
test_60@gmail.com,054PSI_p4hjVVQUUWTxv4Q,"19,223"
```

CSV 2
```
Account Email, YouTube Channel, Subscriber Count
test_1@gmail.com,WBKJ1RNeKTPII34pc6UyUg,29443
test_2@gmail.com,5OXObSqKlu01WtG0GTUq2g,13
test_3@gmail.com,UC7iTbphgUFuJarHcAHMGduQ,1365
test_4@gmail.com,HjA1jv-UJcBxhK_avZfX8Q,5
test_5@gmail.com,lELwfTibQ78MAVyVi6twCg,1477
test_6@gmail.com,1OFDlfdRb6ma1ZGZd07gWA,3590503
test_7@gmail.com,fHRX7ihY8WnSV53NnpKOvQ,54065
test_8@gmail.com,6cf7Ad_qowX9qeQfD5dT8g,"2,831"
test_9@gmail.com,tIRU_vvyQmUADgAt31n7Xg,564
test_10@gmail.com,UCQv9Wo4D2g8tMhH3lGcxiWg,282
test_11@gmail.com,s4cgIKR4SfglgNQGARgsHA,56632
test_12@gmail.com,kRkD16_ps8mZvkZHnby5oA,26582
test_13@gmail.com,pfLKSzjkVsBqIHNbl8Mz6A,428
test_14@gmail.com,oG6lsYx4dhedb0ZjL2O_HQ,5485
test_15@gmail.com,UCXApAnHLoStKPlFR9_KoBKw,689
test_16@gmail.com,UC1eyHg00NjjbFMeF9Ol1Zew,29126
test_17@gmail.com,eiA19nF1mk1YckW5yq8XJQ,8366
test_18@gmail.com,RJ-d6DiO6raIEddFnlrubQ,132
test_19@gmail.com,UCq6N_kqiCjE-KqDmoWgXKYA,26
test_20@gmail.com,33PJanBSN4WfosXHVkA9_A,2371
test_21@gmail.com,https://youtube.com/channel/UCB5ZnX_2hTTP5tTuPmOk3uA,344
test_22@gmail.com,A8E2__IHw9UZhEeHrTEnJA,339
test_23@gmail.com,UCfmVQFPh1KVkCvuvQjnRrxA,"42,953"
test_24@gmail.com,OiVONk5g_VCxXtP2som4yA,172
test_25@gmail.com,ZNw2suHUu1t9NyHB0DolbA,10
test_26@gmail.com,8TRgUb5hGzcPErf5bb1u2Q,3216
test_27@gmail.com,JCM8kLrPjgPcEJEuIV-ELw,1402
test_28@gmail.com,Di_A4XTSiD5hCO3-6R6OqA,2570
test_29@gmail.com,tUCA0-v2fjxOOPyA84nJlg,1434
test_30@gmail.com,zSS4r4fkYgvXL6bWCRwegg,688
test_31@gmail.com,5ZiUupQKOcEx1gvShKS6Bg,25
test_32@gmail.com,fq9aGE_r1TvTfYWpxEI0_Q,180
test_33@gmail.com,6WLScIs2J8VnFulIn79Nfw,534
test_34@gmail.com,8bKzySZjA4Eiir7JvBSkEg,8
test_35@gmail.com,QeUfLM907YOxA_9_jIiung,107
test_36@gmail.com,b95qCSx8rO7U0P0oE6RcvA,503
test_37@gmail.com,w53zi4ftVPYpqKTQUoxfKw,254
test_38@gmail.com,uyFiGMNqQo-nfBX5jY5ZOA,20
test_39@gmail.com,KPsyZ9KQiXktdGK2jRaTwQ,301
test_40@gmail.com,GfCFvRsJfXXgPD1wfrI9wA,644
test_41@gmail.com,e7gOaF5-tH7I3NocgLnhAA,21507
test_42@gmail.com,https://www.youtube.com/channel/UCjXe6LuyALURdEdRBOn8C5A,286
test_43@gmail.com,cLDyZ4ESTq6TQGbc2M1Zig,"112"
test_44@gmail.com,-Zh14hU-5p58lilWNwyQlg,33
test_45@gmail.com,YLCka_OXQZtoBJZ5pW9sFg,31
test_46@gmail.com,_lpDjhfkyaAr1Fd6AoMXQw,100
test_47@gmail.com,EL6PQjvKuk2-6sTaUmub8A,89
test_48@gmail.com,sbo6gAIwSELM1vApwRw4ng,244
test_49@gmail.com,UCX0ZEkd41kOTZ_2qRHViSQw,54
test_50@gmail.com,http://www.youtube.com/channel/UCsR5ZMY4gyAuCUTMkxPocrQ,4
test_51@gmail.com,http://www.youtube.com/channel/UCv3jmHLil11QvVzXxm18KHg,59
test_52@gmail.com,http://www.youtube.com/channel/UChJbZilh7YcrnajYJ-gsLqw,84
test_53@gmail.com,http://www.youtube.com/channel/UCCnms8EieLvB6oNLXBgIGNQ,"13,8902"
test_54@gmail.com,http://www.youtube.com/channel/UCtTIo7Mi2KuZTwoCys4Cdhw,1
test_55@gmail.com,https://www.youtube.com/channel/UCKjvSEotHjQFYjRwCWJGSdQ,5
test_56@gmail.com,youtube.com/channel/UCYVAY2qVpaIzVWA56nIkJtA,766
test_57@gmail.com,youtube.com/channel/UCPhv_Fz6YkjqbWI11IhScOQ,89
test_58@gmail.com,https://www.youtube.com/channel/UCiQ4x3FbxB9yPETGlvevbJQ,246
test_59@gmail.com,http://youtube.com/channel/UCseviT6lqkz1x5rxBoeRZ2g,29
test_60@gmail.com,UC054PSI_p4hjVVQUUWTxv4Q,19223
```