Minecraft Forums

Here is the error script

Bootstrap (v5)
Current time is Feb 10, 2017 9:03:31 PM
System.getProperty('os.name') == 'Linux'
System.getProperty('os.version') == '4.2.0-42-generic'
System.getProperty('os.arch') == 'amd64'
System.getProperty('java.version') == '1.8.0_111'
System.getProperty('java.vendor') == 'Oracle Corporation'
System.getProperty('sun.arch.data.model') == '64'

Downloading: https://s3.amazonaws.com/Minecraft.Download/launcher/launcher.pack.lzma
Exception: javax.net.ssl.SSLHandshakeException: sun.security.validator.ValidatorException: PKIX path building failed: sun.security.provider.certpath.SunCertPathBuilderException: unable to find valid certification path to requested target
Recognized exception: the likely cause is a set of broken/missing root-certificates. Check your java install and perhaps reinstall it.
Downloading: https://s3.amazonaws.com/Minecraft.Download/launcher/launcher.pack.lzma (try 2/10)
Exception: javax.net.ssl.SSLHandshakeException: sun.security.validator.ValidatorException: PKIX path building failed: sun.security.provider.certpath.SunCertPathBuilderException: unable to find valid certification path to requested target
Recognized exception: the likely cause is a set of broken/missing root-certificates. Check your java install and perhaps reinstall it.
Downloading: https://s3.amazonaws.com/Minecraft.Download/launcher/launcher.pack.lzma (try 3/10)
Exception: javax.net.ssl.SSLHandshakeException: sun.security.validator.ValidatorException: PKIX path building failed: sun.security.provider.certpath.SunCertPathBuilderException: unable to find valid certification path to requested target
Recognized exception: the likely cause is a set of broken/missing root-certificates. Check your java install and perhaps reinstall it.
Downloading: https://s3.amazonaws.com/Minecraft.Download/launcher/launcher.pack.lzma (try 4/10)
Exception: javax.net.ssl.SSLHandshakeException: sun.security.validator.ValidatorException: PKIX path building failed: sun.security.provider.certpath.SunCertPathBuilderException: unable to find valid certification path to requested target
Recognized exception: the likely cause is a set of broken/missing root-certificates. Check your java install and perhaps reinstall it.
Downloading: https://s3.amazonaws.com/Minecraft.Download/launcher/launcher.pack.lzma (try 5/10)
Exception: javax.net.ssl.SSLHandshakeException: sun.security.validator.ValidatorException: PKIX path building failed: sun.security.provider.certpath.SunCertPathBuilderException: unable to find valid certification path to requested target
Recognized exception: the likely cause is a set of broken/missing root-certificates. Check your java install and perhaps reinstall it.
Downloading: https://s3.amazonaws.com/Minecraft.Download/launcher/launcher.pack.lzma (try 6/10)
Exception: javax.net.ssl.SSLHandshakeException: sun.security.validator.ValidatorException: PKIX path building failed: sun.security.provider.certpath.SunCertPathBuilderException: unable to find valid certification path to requested target
Recognized exception: the likely cause is a set of broken/missing root-certificates. Check your java install and perhaps reinstall it.
Downloading: https://s3.amazonaws.com/Minecraft.Download/launcher/launcher.pack.lzma (try 7/10)
Exception: javax.net.ssl.SSLHandshakeException: sun.security.validator.ValidatorException: PKIX path building failed: sun.security.provider.certpath.SunCertPathBuilderException: unable to find valid certification path to requested target
Recognized exception: the likely cause is a set of broken/missing root-certificates. Check your java install and perhaps reinstall it.
Downloading: https://s3.amazonaws.com/Minecraft.Download/launcher/launcher.pack.lzma (try 8/10)
Exception: javax.net.ssl.SSLHandshakeException: sun.security.validator.ValidatorException: PKIX path building failed: sun.security.provider.certpath.SunCertPathBuilderException: unable to find valid certification path to requested target
Recognized exception: the likely cause is a set of broken/missing root-certificates. Check your java install and perhaps reinstall it.
Downloading: https://s3.amazonaws.com/Minecraft.Download/launcher/launcher.pack.lzma (try 9/10)
Exception: javax.net.ssl.SSLHandshakeException: sun.security.validator.ValidatorException: PKIX path building failed: sun.security.provider.certpath.SunCertPathBuilderException: unable to find valid certification path to requested target
Recognized exception: the likely cause is a set of broken/missing root-certificates. Check your java install and perhaps reinstall it.
Downloading: https://s3.amazonaws.com/Minecraft.Download/launcher/launcher.pack.lzma (try 10/10)
Exception: javax.net.ssl.SSLHandshakeException: sun.security.validator.ValidatorException: PKIX path building failed: sun.security.provider.certpath.SunCertPathBuilderException: unable to find valid certification path to requested target
Recognized exception: the likely cause is a set of broken/missing root-certificates. Check your java install and perhaps reinstall it.
Unable to download remote file. Check your internet connection/proxy settings.
FATAL ERROR: net.minecraft.bootstrap.FatalBootstrapError: Unable to download while being forced
at net.minecraft.bootstrap.Bootstrap.execute(Bootstrap.java:95)
at net.minecraft.bootstrap.Bootstrap.main(Bootstrap.java:381)

Please fix the error and restart.

The SSL connection is being made with either a missing certificate in your pc or a wrong one in the server, try adding it back to they keystore

I fixed it by running in terminal:

sudo update-ca-certificates -f

Because that adds it for you :P, glad it works!