Failed installation of Avast

Question

Trying to install the latest Avast on a MBA running 10.9.5. No sign of any problems. Machine running fine. I had installed Avast on another machine of his and it did some good, so he wanted it on his MBAir.
The problem, the installer fails at the final stage with a completely generic message that's no help.
Looking at the console log, lead me to believe a couple things:
- Perhaps it was tripping over a permission problem.
- or perhaps it wasn’t happy that Chrome was not installed.
One specific log line item says (which might be the key if someone can interpret, my Google searches haven't been able to untangle):
"CoreServicesUIAgent: Error: qtn_file_apply_to_path error: Read-only file system"
So, here are the things the DIDN'T solve the problem
1) repaired permissions
2) installed Chrome
3) repaired home permissions
4) restarted
5) turned off Gatekeeper
6) redownloaded installer
7) ran Disk Repair, which led me to booting into Recovery Mode to fix a couple directory structure mismatches.
Any ideas what else it could be tripping up this install?
I don’t have enough experience with Avast to know whether or not this is an “Avast problem”, but I certainly have more experience with installing under Mavericks to say Avast is most likely the culprit here.
I suppose I could give up on Avast and go to ClamAV, but he’s “sold” on Avast. I realize there are other virus protection solutions and I realize there's some debate on whether or not anti-virus software SHOULD be installed on a Mac. Just looking for suggestions on the installation problem itself.
Have submitted a ticket to Avast, but only a canned response so far.

Answer 1

Non-Apple "anti-virus" products are worthless and will prevent your Mac from working as designed. Some such products are malicious. "Avast" is not the worst of them, but it comes close.
Nothing in the world can prevent you from succumbing from "phishing" scams.
There will always be threats to your information security associated with using any Internet - connected communications tool:
You can mitigate those threats by following commonsense practices
Delegating that responsibility to software is an ineffective defense
Assuming that any product will protect you from those threats is a hazardous attitude that is likely to result in neglecting point #1 above.
OS X already includes everything it needs to protect itself from viruses and malware. Keep it that way with software updates from Apple.
A much better question is "how should I protect my Mac":
Never install any product that claims to "clean up", "speed up", "optimize", "boost" or "accelerate" your Mac; to "wash" it, "tune" it, or to make it "shiny". Those claims are absurd.Such products are very aggressively marketed. They are all scams.
Never install pirated or "cracked" software, software obtained from dubious websites, or other questionable sources.
Illegally obtained software is almost certain to contain malware.
"Questionable sources" include but are not limited to spontaneously appearing web pages or popups, download hosting sites such as C net dot com, Softonic dot com, Soft pedia dot com, Download dot com, Mac Update dot com, or any other site whose revenue is primarily derived from junk product advertisements.
If you need to install software that isn't available from the Mac App Store, obtain it only from legitimate sources authorized by the software's developer.
Don’t supply your password in response to a popup window requesting it, unless you know what it is and the reason your credentials are required.
Don’t open email attachments from email addresses that you do not recognize, or click links contained in an email:
Most of these are scams that direct you to fraudulent sites that attempt to convince you to disclose personal information.
Such "phishing" attempts are the 21st century equivalent of a social exploit that has existed since the dawn of civilization. Don’t fall for it.
Apple will never ask you to reveal personal information in an email. If you receive an unexpected email from Apple saying your account will be closed unless you take immediate action, just ignore it. If your iCloud, iTunes, or App Store account becomes disabled for valid reasons, you will know when you try to buy something or log in to this support site, and are unable to.
Don’t install browser extensions unless you understand their purpose:Go to the Safari menu > Preferences > Extensions. If you see any extensions that you do not recognize or understand, simply click the Uninstall button and they will be gone.
Don’t install Java unless you are certain that you need it:
Java, a non-Apple product, is a potential vector for malware. If you are required to use Java, be mindful of that possibility.
Java can be disabled in System Preferences.
Despite its name JavaScript is unrelated to Java. No malware can infect your Mac through JavaScript. It’s OK to leave it enabled.
The same precaution applies to Adobe Flash Player. Newly discovered Flash vulnerabilities appear almost weekly.
Beware spontaneous popups: Safari menu > Preferences > Security > check "Block popup windows".
Popup windows are useful and required for some websites, but unsolicited popups are commonly used to deceive people into installing unwanted software they would never intentionally install.
Popups themselves cannot infect your Mac, but many contain resource-hungry code that will slow down Internet browsing.
If you ever receive a popup window indicating that your Mac is infected with some ick or that you won some prize, it is 100% fraudulent. Ignore it.
The same goes for a spontaneously appearing dialog insisting that you upgrade your video player right this instant. Such popups are frequently associated with sites that promise to deliver "free" movies or other copyrighted content that is not normally "free".
The more insistent it is that you upgrade or install something, the more likely it is to be a scam. Close the window or tab and forget it.
Ignore hyperventilating popular media outlets that thrive by promoting fear and discord with entertainment products arrogantly presented as "news". Learn what real threats actually exist and how to arm yourself against them:
The most serious threat to your data security is phishing. Most of these attempts are pathetic and are easily recognized, but that hasn't stopped prominent public figures from recently succumbing to this age-old scam.
OS X viruses do not exist, but intentionally malicious or poorly written code, created by either nefarious or inept individuals, is nothing new.
Never install something without first knowing what it is, what it does, how it works, and how to get rid of it when you don’t want it any more.
If you elect to use "anti-virus" software, familiarize yourself with its limitations and potential to cause adverse effects, and apply the principle immediately preceding this one.
Most such utilities will only slow down and destabilize your Mac while they look for viruses that do not exist, conveying no benefit whatsoever - other than to make you "feel good" about security, when you should actually be exercising sound judgment, derived from accurate knowledge, based on verifiable facts.
Do install updates from Apple as they become available. No one knows more about Macs and how to protect them than the company that builds them.
Summary: Use common sense and caution when you use your Mac, just like you would in any social context. There is no product, utility, or magic talisman that can protect you from all the evils of mankind.